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Carl Sagan 

The Cosmic Connection 

An Extraterrestrial Perspective 

Published by 


1 Dag Hammarskjold Plaza 
New York, New York 10017 
Copyright © 1973 by Carl Sagan and Jerome Agel 
All rights reserved. For information contact 
Doubleday & Company, Inc., New York, New York 
Dell ® TM 681510, Dell Publishing Co., Inc. 

Reprinted by arrangement with Doubleday & Company, Inc. 

Printed in the United States of America 
First Dell printing-March 1975 

Dr. Carl Sagan, the author of The Cosmic Connection, is Professor of Astronomy and Space Sciences and 
Director of the Laboratory for Planetary Studies at Cornell University. He received NASA's Medal for 
Exceptional Scientific Achievement for his studies of Mars with Mariner 9; he was responsible for 
placing the message from Earth aboard the interstellar spacecraft Pioneer 10; and he chaired the U.S. 
delegation to the U.S./U.S.S.R. Conference on Communication with Extraterrestrial Intelligence. Dr. 
Sagan was awarded in 1973 the Prix Galabert — the international astronautics prize. He is editor of the 
planetary science journal Icarus and is widely known for his studies of the planets, the origin of life, and 
the prospects for life beyond the Earth. He is formerly of the Harvard, Caltech and Stanford Medical 

School faculties. 

Jerome Agel is the producer of The Cosmic Connection. His fourteen book productions include: Herman 
Kahnsciousness, Understanding Understanding (with Humphrey Osmond), The Medium Is the Massage 
(with Marshall McLuhan), The Making of Kubrick's "2001," Is Today Tomorrow ? (a synergistic collage of 
alternative futures), I Seem to Be a Verb (with Buckminster Fuller), A World Without — What Our 
Presidents Didn't Know, Surprising Facts About U.S. History, Right on Time (with Alan Lakein), The 
Fasting Diet: How to Lose Weight Without Eating (with Allan Cott), and Rough Times. 


For Dorion, Jeremy, and Nicholas, my sons. May their future - and the future of 
all human and other beings - be bright with promise. 





1. A Transitional Animal 

2. The Unicorn of Cetus 
2. A Message from Earth 
4. A Message to Earth 

2. Experiments in Utopias 

6. Chauvinism 

7. Space Exploration as a I lurnan Enterprise 

I. The Scientific Interest 

8. Space Exploration as a Human Enterprise 

II. The Public Interest 

o. Space Exploration as a Human Enterprise 

III. The Historical Interest 


10. On Teaching the First Grade 

11. "The Ancient and Legendary Gods of Old" 

12. The Venus Detective Story 
17. Venus Is Hell 

14. Science and "Intelligence" 

1 2. The Moons of Barsoom 

16. The Mountains of Mars 

I. Observations From Earth 

17. The Mountains of Mars 

II. Observations From Space 

18. The Canals of Mars 

iq. The Lost Pictures of Mars 

20. The Ice Age and the Cauldron 

21. Beginnings and Ends of the Earth 

22. Terraforming the Planets 

27. The Exploration and Utilization of the Solar System 


2 a . Some of My Best Friends Are Dolphins 

25. "Hello. Central Casting? Send Me Twenty Extraterrestrials" 

26. The Cosmic Connection 

27. Extraterrestrial Life: An Idea Whose Time Has Come 

28. Has the Earth Been Visited? 

2Q. A Search Strategy for Detecting Extraterrestrial Intelligence 

70. If We Succeed 

71. Cables. Drums, and Seashells 

72. The Night Freight to the Stars 
22. Astroengineering 

74. Twenty Questions: A Classification of Cosmic Civilizations 
22. Galactic Cultural Exchanges 

26. A Passage to Elsewhen 

27 . Starfolk 

I. A Fable 
78. Starfolk 

II. A Future 
7Q. Starfolk 

The Cosmic Cheshire Cats 


"Les Myxtfaes des Infirm" by Grandville, 1844. 



When I was twelve, my grandfather asked me - through a translator (he had 
never learned much English) - what I wanted to be when I grew up. I answered, 
"An astronomer," which, after a while, was also translated. "Yes," he replied, "but 
how will you make a living?" 

I had supposed that, like all the adult men I knew, I would be consigned to a 
dull, repetitive, and uncreative job, astronomy would be done on weekends. It was 
not until my second year in high school that I discovered that some astronomers 
were paid to pursue their passion. I was overwhelmed with joy; I could pursue my 
interest full-time. 

Even today, there are moments when what I do seems to me like an 
improbable, if unusually pleasant, dream: To be involved in the exploration of 
Venus, Mars, Jupiter, and Saturn; to try to duplicate the steps that led to the 
origin of life four billion years ago on an Earth very different from the one we 
know; to land instruments on Mars to search there for life; and perhaps to be 
engaged in a serious effort to communicate with other intelligent beings, if such 
there be, out there in the dark of the night sky. 

Had I been born fifty years earlier, I could have pursued none of these 
activities. They were then all figments of the speculative imagination. Had I been 
born fifty years later, I also could not have been involved in these efforts, except 
possibly the last, because fifty years from now the preliminary reconnaissance of 
the Solar System, the search for life on Mars, and the study of the origin of life will 
have been completed. I think myself extraordinarily fortunate to be alive at the 
one moment in the history of mankind when such ventures are being undertaken. 

So when Jerome Agel approached me about doing a popular book to try to 
communicate my sense of the excitement and importance of these adventures, I 
was amenable - even though his suggestion came just before the Mariner 9 
mission to Mars, which I knew would occupy most of my waking hours for many 
months. At a later time, after discussing communication with extraterrestrial 
intelligence, Agel and I had dinner in a Polynesian restaurant in Boston. My fortune 
cookie announced, "You will shortly be called upon to decipher an important 
message." This seemed a good omen. 

After centuries of muddy surmise, unfettered speculation, stodgy conservatism, 
and unimaginative disinterest, the subject of extraterrestrial life has finally come of 
age. It has now reached a practical stage where it can be pursued by rigorous 
scientific techniques, where it has achieved scientific respectability and where its 
significance is widely understood. Extraterrestrial life is an idea whose time has 

This book is divided into three major sections. In the first part I try in several 
ways to convey a sense of cosmic perspective — living out our lives on a tiny hunk 
of rock and metal circling one of 250 billion stars that make up our galaxy in a 
universe of billions of galaxies. The deflation of some of our more common 


conceits is one of the practical applications of astronomy. The second part of the 
book is concerned with various aspects of our Solar System - mostly with Earth, 
Mars, and V enus. Some of the results and implications of Mariner g can be found 
here. Part Three is devoted to the possibility of communicating with 
extraterrestrial intelligence on planets of other stars. Since no such contact has yet 
been made - our efforts to date have been feeble — this section is necessarily 
speculative. I have not hesitated to speculate within what I perceive to be the 
bounds of scientific plausibility. And, although I am not by training a philosopher 
or sociologist or historian, I have not hesitated to draw philosophical or social or 
historical implications of astronomy and space exploration. 

The astronomical discoveries we are in the midst of making are of the broadest 
human significance. If this book plays a small role in broadening public 
consideration of these exploratory ventures, it will have served its purpose. 

As with all ongoing work and especially all speculative subjects, some of the 
statements in these pages will elicit vigorous demurrers. There are other books 
with other opinions. Reasoned disputation is the lifeblood of science - as is, sadly, 
infrequently the case in the intellectually more anemic arena of politics. But I 
believe that the more controversial opinions expressed here have, nevertheless, a 
significant scientific constituency. I have purposely introduced the same concept 
in slightly different contexts in a few places where I felt the discussion required it. 
The book is carefully structured, but, for the reader who wishes to browse ahead, 
most chapters are self-contained. 

There are far too many who helped shape my opinions on these subjects for 
me to thank them all here. But in rereading these chapters, I find I owe a special 
debt to Joseph Veverka and Frank Drake, both of Cornell University, with whom 
over the past few years I have discussed so many aspects of this volume. The book 
was composed partly during a very long transcontinental trip in a very short 
automobile. I thank Linda and Nicholas for their encouragement and patience. I 
am also grateful to Linda for drawing two handsome humans and one elegant 
unicorn. And I am grateful to the late Mauritz Escher for permission to reproduce 
his "Another World" and to Robert Macintyre for the human figure and star field 
in Part Three. Jon Lomberg's paintings and drawings have been a source of 
intellectual and aesthetic excitement for me, and I am grateful to him for 
producing many of them especially for this book. Hermann Eckleman's careful 
photographic reproductions of Lomberg's work have facilitated their appearance 
in this book. And I thank Jerome Agel, without whose time and persistence this 
book would never have been written. 

I am indebted to John Naugle of NASA for showing me his file on public 
response to the Pioneer io plaque; the Oregon System of Higher Education for 
permission to reproduce some ideas from my book Planetary Exploration; the 
Forum for Contemporary History, in Santa Barbara, for permission to reproduce a 
portion of my letter distributed by the Forum in January 1973; and Cornell 
University Press for permission to reprint a fraction of my chapter "The 


Extraterrestrial and Other Hypotheses" from UFO's: A Scientific Debate, edited by 
Carl Sagan and Thornton Page, Cornell University Press, 1972. I am also grateful to 
those who have granted me permission to reproduce in Chapter 4 their remarks 
on the Pioneer 10 plaque. The evolution of this book through many drafts owes 
much to the technical skills of Jo Ann Cowan, and, especially, Mary Szymanski. 

- Carl Sagan 


Part One: 


We shall not cease from exploration 
And the end of all our exploring 
Will be to arrive where we started 
And know the place for the first time. . . 
When the tongues of flame are in-folded 
Into the crowned knot of fire 
And the fire and the rose are one. 

- T. S. Eliot, Four Quartets 

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i. A Transitional Animal 

Five billion years ago, when the Sun turned on, the Solar System was transformed 
from inky blackness to a flood of light. In the inner parts of the Solar System, the 
early planets were irregular collections of rock and metal - the debris, the minor 
constituents of the initial cloud, the material that had not been blown away after 
the Sun ignited. 

These planets heated as they formed. Gases trapped in their interiors were 
exuded to form atmospheres. Their surfaces melted. Volcanoes were common. 

The early atmospheres were composed of the most abundant atoms and were 
rich in hydrogen. Sunlight, falling on the molecules of the early atmosphere, 
excited them, induced molecular collisions, and produced larger molecules. Under 
the inexorable laws of chemistry and physics these molecules interacted, fell into 
the oceans, and further developed to produce larger molecules - molecules much 
more complex than the initial atoms of which they had formed, but still 
microscopic by any human standard. 

These molecules, remarkably enough, are the ones of which we are made: The 
building blocks of the nucleic acids, which are our hereditary material, and the 
building blocks of the proteins, the molecular journeymen that perform the work 
of the cell, were produced from the atmosphere and oceans of the early Earth. We 
know this because we can make these molecules today by duplicating the 
primitive conditions. 

Eventually, many billions of years ago, a molecule was formed that had a 
remarkable capability. It was able to produce, out of the molecular building blocks 
of the surrounding waters, a fairly accurate copy of itself. In such a molecular 
system there is a set of instructions, a molecular code, containing the sequence of 
building blocks from which the larger molecule is constructed. When, by accident, 
there is a change in the sequence, the copy is likewise changed. Such a molecular 
system — capable of replication, mutation, and replication of its mutations - can be 
called "alive." It is a collection of molecules that can evolve by natural selection. 
Those molecules able to replicate faster, or to reprocess building blocks from their 
surroundings into a more useful variety, reproduced more efficiently than their 
competitors - and eventually dominated. 

But conditions gradually changed. Hydrogen escaped to space. Production of 
the molecular building blocks declined. The foodstuffs formerly available in great 
abundance dwindled. Life was expelled from the molecular Garden of Eden. Only 
those simple collections of molecules able to transform their surroundings, able to 
produce efficient molecular machines for the conversion of simple into complex 
molecules, were able to survive. By isolating themselves from their surroundings, 
by maintaining the earlier idyllic conditions, those molecules that surrounded 
themselves by membranes had an advantage. The first cells arose. 

With molecular building blocks no longer available for free, organisms had to 
work hard to make such building blocks. Plants are the result. Plants start with air 


and water, minerals and sunlight, and produce molecular building blocks of high 
complexity. Animals, such as human beings, are parasites on the plants. 

Changing climate and competition among what was now a wide diversity of 
organisms produced greater and greater specialization, a sophistication of function, 
and an elaboration of form. A rich array of plants and animals began to cover the 
Earth. Out of the initial oceans in which life arose, new environments, such as the 
land and the air, were colonized. Organisms now live from the top of Mount 
Everest to the deepest portions of the abyssal depths. Organisms live in hot, 
concentrated solutions of sulfuric acid and in dry Antarctic valleys. Organisms live 
on the water adsorbed on a single crystal of salt. 

Life forms developed that were finely attuned to their specific environments, 
exquisitely adapted to the conditions. But the conditions changed. The organisms 
were too specialized. They died. Other organisms were less well adapted, but they 
were more generalized. The conditions changed, the climate varied, but the 
organisms were able to continue. Many more species of organisms have died 
during the history of the Earth than are alive today. The secret of evolution is time 
and death. 

Among the adaptations that seem to be useful is one that we call intelligence. 
Intelligence is an extension of an evolutionary tendency apparent in the simplest 
organisms — the tendency toward control of the environment. The standby 
biological method of control has been the hereditary material: Information passed 
on by nucleic acids from generation to generation - information on how to build a 
nest; information on the fear of falling, or of snakes, or of the dark; information on 
how to fly south for the winter. But intelligence requires information of an 
adaptive quality developed during the lifetime of a single individual. A variety of 
organisms on the Earth today have this quality we call intelligence: The dolphins 
have it, and so do the great apes. But it is most evident in the organism called Man. 

In Man, not only is adaptive information acquired in the lifetime of a single 
individual, but it is passed on extra-genetically through learning, through books, 
through education. It is this, more than anything else, that has raised Man to his 
present pre-eminent status on the planet Earth. 

We are the product of 4.5 billion years of fortuitous, slow, biological evolution. 
There is no reason to think that the evolutionary process has stopped. Man is a 
transitional animal. He is not the climax of creation. 

The Earth and the Sun have life expectancies of many more billions of years. 
The future development of man will likely be a cooperative arrangement among 
controlled biological evolution, genetic engineering, and an intimate partnership 
between organisms and intelligent machines. But no one is in a position to make 
accurate predictions of this future evolution. All that is clear is that we cannot 
remain static. 

In our earliest history, so far as we can tell, individuals held an allegiance 
toward their immediate tribal group, which may have numbered no more than ten 
or twenty individuals, all of whom were related by consanguinity. As time went 


on, the need for cooperative behavior - in the hunting of large animals or large 
herds, in agriculture, and in the development of cities - forced human beings into 
larger and larger groups. The group that was identified with, the tribal unit, 
enlarged at each stage of this evolution. Today, a particular instant in the 4.5- 
billion-year history of Earth and in the several-million-year history of mankind, 
most human beings owe their primary allegiance to the nation-state (although 
some of the most dangerous political problems still arise from tribal conflicts 
involving smaller population units) . 

Many visionary leaders have imagined a time when the allegiance of an 
individual human being is not to his particular nation-state, religion, race, or 
economic group, but to mankind as a whole; when the benefit to a human being 
of another sex, race, religion, or political persuasion ten thousand miles away is as 
precious to us as to our neighbor or our brother. The trend is in this direction, but 
it is agonizingly slow. There is a serious question whether such a global self- 
identification of mankind can be achieved before we destroy ourselves with the 
technological forces our intelligence has unleashed. 

In a very real sense human beings are machines constructed by the nucleic 
acids to arrange for the efficient replication of more nucleic acids. In a sense our 
strongest urges, noblest enterprises, most compelling necessities, and apparent free 
wills are all an expression of the information coded in the genetic material: We 
are, in a way, temporary ambulatory repositories for our nucleic acids. This does 
not deny our humanity; it does not prevent us from pursuing the good, the true, 
and the beautiful. But it would be a great mistake to ignore where we have come 
from in our attempt to determine where we are going. 

There is no doubt that our instinctual apparatus has changed little from the 
hunter- gatherer days of several hundred thousand years ago. Our society has 
changed enormously from those times, and the greatest problems of survival in the 
contemporary world can be understood in terms of this conflict - between what 
we feel we must do because of our primeval instincts and what we know we must 
do because of our extragenetic learning. 

If we survive these perilous times, it is clear that even an identification with all 
of mankind is not the ultimate desirable identification. If we have a profound 
respect for other human beings as co-equal recipients of this precious patrimony 
of 4.5 billion years of evolution, why should the identification not apply also to all 
the other organisms on Earth, which are equally the product of 4.5 billion years of 
evolution? W e care for a small fraction of the organisms on Earth - dogs, cats, and 
cows, for example - because they are useful or because they flatter us. But spiders 
and salamanders, salmon and sunflowers are equally our brothers and sisters. 

I believe that the difficulty we all experience in extending our identification 
horizons in this way is itself genetic. Ants of one tribe will fight to the death 
intrusions by ants of another. Human history is filled with monstrous cases of 
small differences - in skin pigmentation, or abstruse theological speculation, or 


manner of dress and hair style - being the cause of harassment, enslavement, and 

A being quite like us, but with a small physiological difference - a third eye, 
say, or blue hair covering the nose and forehead - somehow evokes feelings of 
revulsion. Such feelings may have had adaptive value at one time in defending our 
small tribe against the beasts and neighbors. But in our times, such feelings are 
obsolete and dangerous. 

The time has come for a respect, a reverence, not just for all human beings, but 
for all life forms - as we would have respect for a masterpiece of sculpture or an 
exquisitely tooled machine. This, of course, does not mean that we should 
abandon the imperatives for our own survival. Respect for the tetanus bacillus 
does not extend to volunteering our body as a culture medium. But at the same 
time we can recall that here is an organism with a biochemistry that tracks back 
deep into our planet's past. The tetanus bacillus is poisoned by molecular oxygen, 
which we breathe so freely. The tetanus bacillus, but not we, would be at home in 
the hydrogen-rich, oxygen-free atmosphere of primitive Earth. 

A reverence for all life is implemented in a few of the religions of the planet 
Earth - for example, among the Jains of India. And something like this idea is 
responsible for vegetarianism, at least in the minds of many practitioners of this 
dietary constraint. But why is it better to kill plants than animals? 

Human beings can survive only by killing other organisms. But we can make 
ecological compensation by also growing other organisms; by encouraging the 
forest; by preventing the wholesale slaughter of organisms such as seals and 
whales, imagined to have industrial or commercial value; by outlawing gratuitous 
hunting, and by making the environment of Earth more livable - for all its 

There may be a time, as I describe in Part III of this book, when contact will be 
made with another intelligence on a planet of some far-distant star, beings with 
billions of years of quite independent evolution, beings with no prospect of 
looking very much like us - although they may think very much like us. It is 
important that we extend our identification horizons, not just down to the 
simplest and most humble forms of life on our own planet, but also up to the 
exotic and advanced forms of life that may inhabit, with us, our vast galaxy of 

2. The Unicorn of Cetus 

In the night sky, when the air is clear, there is a cosmic Rorschach test awaiting us. 
Thousands of stars, bright and faint, near and far, in a glittering variety of colors, 
are peppered across the canopy of night The eye, irritated by randomness, seeking 
order, tends to organize into patterns these separate and distinct points of light. 
Our ancestors of thousands of years ago, who spent almost all their time out of 
doors in a pollution-free atmosphere, studied these patterns carefully. A rich 
mythological lore evolved. 

Much of the original substance of this stellar mythology has not come down to 
us. It is so ancient, has been retold so many times, and especially in the past few 
thousand years by individuals unfamiliar with the appearance of the sky, that 
much has been lost. Here and there, in odd places, there remain some echoes of 
cosmic stories about patterns in the sky. 

In the Book of Judges there is an account of a slain lion discovered to be 
infested by a hive of bees, a strange and apparently pointless incident. But the 
constellation of Leo in the night sky is adjacent to a cluster of stars, visible on a 
clear night as a fuzzy patch of light, called Praesepe. From its telescopic 
appearance, modern astronomers call it "The Beehive." I wonder if an image of 
Praesepe, obtained by one man of exceptional eyesight, in days before the 
telescope, has been preserved for us in the Book of Judges. 

When I look out into the night sky, I cannot discern the outline of a lion in the 
constellation Leo. I can make out the Big Dipper, and, if the night is clear, the 
Little Dipper. I am at a loss to make out much of a hunter in Orion or a fish in the 
constellation of Pisces, to say nothing of a charioteer in Auriga. The mythical 
beasts, personages, and instruments placed by men in the sky are arbitrary, not 
obvious. There are agreements about which constellation is which — sanctioned in 
recent years by the International Astronomical Union, which draws boundaries 
separating one constellation from another. But there are few clear pictures in the 

These constellations, while drawn in two dimensions, are fundamentally in 
three dimensions. A constellation, such as Orion, is composed of bright stars at 
considerable distances from Earth and dim stars much closer. Were we to change 
our perspective, move our point of view - with, for example, an interstellar space 
vehicle - the appearance of the sky would change. The constellations would 
slowly distort. 

Largely through the efforts of David Wallace at the Laboratory for Planetary 
Studies at Cornell University, an electronic computer has been programmed with 
the information on the three-dimensional positions from the Earth to each of the 
brightest and nearest stars - down to about fifth magnitude, the limiting brightness 
visible to the naked eye on a clear night. When we ask the computer to show us 
the appearance of the sky from Earth, we see results of the sort displayed in the 
accompanying figures: One for the northern circumpolar constellations, including 


the Big Dipper, the Little Dipper, and Cassiopeia; one for the southern 
circumpolar constellations, including the Southern Cross; and one for the broad 
range of stars at middle celestial latitudes, including Orion and the constellations of 
the zodiac. If you are not a student of the conventional constellations, you will, I 
believe, have some difficulty making out scorpions or virgins in the picture. 


The constellations of the northern sky a* seen from the vi- 
cinity of the Sun or the Earth. 

We now ask the computer to draw us the sky from the nearest star to our 
own, Alpha Centauri, a triple-star system, about 4.3 light-years from Earth. In 
terms of the scale of our Milky Way Galaxy, this is such a short distance that our 
perspectives remain almost exactly the same. From a Cen the Big Dipper appears 
just as it does from Earth. Almost all the other constellations are similarly 
unchanged. There is one striking exception, however, and that is the constellation 
Cassiopeia. Cassiopeia, the queen of an ancient kingdom, mother of Andromeda 
and mother-in-law of Perseus, is mainly a set of five stars arranged as a W or an M, 
depending on which way the sky has turned. From Alpha Centauri, however, 
there is one extra jog in the M; a sixth star appears in Cassiopeia, one significantly 
brighter than the other five. That star is the Sun. From the vantage point of the 
nearest star, our Sun is a relatively bright but unprepossessing point in the night 
sky. There is no way to tell by looking at Cassiopeia from the sky of a hypothetical 
planet of Alpha Centauri that there are planets going around the Sun, that on the 
third of these planets there are life forms, and that one of these life forms 
considers itself to be of quite considerable intelligence. If this is the case for the 
sixth star in Cassiopeia, might it not also be the case for innumerable millions of 
other stars in the night sky? 



The same scene as viewed from the nearest star. Alpha 
Centauri. The new star in the constellation of Cassiopeia, 
near 60 degrees celestial latitude and 2.5 hours celestial 
longitude, is the Sun. 

One of the two stars that Project Ozma examined a decade ago for possible 
extraterrestrial intelligent signals was Tau Ceti, in the constellation (as seen from 
Earth) of Cetus, the whale. In the accompanying figure, the computer has drawn 
the sky as seen from a hypothetical planet of T Cet. We are now a little more than 
eleven light-years away from the Sun. The perspective has changed somewhat 
more. The relative orientation of the stars has varied, and we are free to invent 
new constellations - a psychological projective test for the Cetians. 




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The brightest Mara, as seen from the Earth and Sun. which 
are not in the vicinity of the North or South Celestial Poles. 

I asked my wife, Linda, who is an artist, to draw a constellation of a unicorn in 
the Cetian sky. There is already a unicorn in our sky, called Monoceros, but I 
wanted this to be a larger and more elegant unicorn - and also one slightly 
different from common terrestrial unicorns - with six legs, say, rather than four. 
She invented quite a handsome beast. Contrary to my expectation that he would 
have three pairs of legs, he is quite proudly galloping on two clusters of three legs 
each, one fore and one aft. It seems quite a believable gallop. There is a tiny star 
that is just barely seen at the point where the unicorn's tail joins the rest of his 
body. That faint and un-inspiringly positioned star is the Sun. The Cetians may 
consider it an amusing speculation that a race of intelligent beings lives on a planet 
circling the star that joins the unicorn to his tail. 



The same stars as seen on opposite page but front the vantage 
point of Tau Ceti, one of the nearest stars like the Sun. In 
the sky of Tau Ceti, the Sun is a fourth magnitude star. 

When we move to greater distances from the Sun than Tau Ceti - to forty or 
fifty light-years - the Sun dwindles still further in brightness until it is invisible to 
an unaided human eye. Long interstellar voyages - if they are ever undertaken - 
will not use dead-reckoning on the Sun. Our mighty star, on which all life on Earth 
depends, our Sun, which is so bright that we risk blindness by prolonged direct 
viewing, cannot be seen at all at a distance of a few dozen light-years - a 
thousandth of the distance to the center of our Galaxy. 


3. A Message from Earth 

Mankind's first serious attempt to communicate with extraterrestrial civilizations 
occurred on March 3, 1972, with the launching of the Pioneer 10 spacecraft from 
Cape Kennedy. Pioneer 10 was the first space vehicle designed to explore the 
environment of the planet Jupiter and, earlier in its voyage, the asteroids that lie 
between the orbits of Mars and Jupiter. Its orbit was not disturbed by an errant 
asteroid - the safety factor was estimated as 20 to 1. It approached Jupiter on 
December 3, 1973, and then was accelerated by Jupiter's gravity to become the 
first man-made object to leave the Solar System. Its exit velocity is about 7 miles 
per second. 

Pioneer 10 is the speediest object launched to date by mankind. But space is 
very empty, and the distances between the stars are vast. In the next 10 billion 
years, Pioneer 10 will not enter the planetary system of any other star, even 
assuming that all the stars in the Galaxy have such planetary systems. The 
spacecraft will take about 80,000 years merely to travel the distance to the nearest 
star, about 4.3 light-years away. 

But Pioneer 10 is not directed to the vicinity of the nearest star. Instead, it will 
be traveling toward a point on the celestial sphere near the boundary of the 
constellations Taurus and Orion, where there are no nearby objects. 

It is conceivable that the spacecraft will be encountered by an extraterrestrial 
civilization only if such a civilization has an extensive capability for interstellar 
space flight and is able to intercept and recover such silent space derelicts. 

Placing a message aboard Pioneer 10 is very much like a shipwrecked sailor 
casting a bottled message into the ocean - but the ocean of space is much vaster 
than any ocean on Earth. 

When my attention was drawn to the possibility of placing a message in a 
space-age bottle, I contacted the Pioneer 10 project office and NASA headquarters 
to see if there were any likelihood of implementing this suggestion. T o my surprise 
and delight, the idea met with approval at all steps up the NASA hierarchy, 
despite the fact that it was - by ordinary standards - very late to make even tiny 
changes in the spacecraft. During a meeting of the American Astronomical Society 
in San Juan, Puerto Rico, in December 1971, I discussed privately various possible 
messages with my colleague Professor Frank Drake, also of Cornell. In a few hours 
we decided tentatively on the contents of the message. The human figures were 
added by my artist wife, Linda Salzman Sagan. We do not think it is the optimum 
conceivable message for such a purpose: There were a total of only three weeks 
for the presentation of the idea, the design of the message, its approval by NASA, 
and the engraving of the final plaque. An identical plaque has been launched in 
1973 on the Pioneer n spacecraft, on a similar mission. 

On the title page of this chapter is shown the message. It is etched on a 6-inch 
by 9-inch gold-anodized aluminum plate, attached to the antenna support struts of 
Pioneer 10. The expected erosion rate in interstellar space is sufficiently small that 


this message should remain intact for hundreds of millions of years, and probably 
for a much longer period of time. It is, thus, the artifact of mankind with the 
longest expected lifetime. 

The message itself intends to communicate the locale, epoch, and something of 
the nature of the builders of the spacecraft. It is written in the only language we 
share with the recipients: Science. At top left is a schematic representation of the 
hyperfine transition between parallel and antiparallel proton and electron spins of 
the neutral hydrogen atom. Beneath this representation is the binary number 1. 
Such transitions of hydrogen are accompanied by the emission of a radio- 
frequency photon of wavelength about 21 centimeters and frequency of about 
1,420 Megahertz. Thus, there is a characteristic distance and a characteristic time 
associated with the transition. Since hydrogen is the most abundant atom in the 
Galaxy, and physics is the same throughout the Galaxy, we think there will be no 
difficulty for an advanced civilization to understand this part of the message. But 
as a check, on the right margin is the binary number 8 (1—) between two tote 
marks, indicating the height of the Pioneer 10 spacecraft, schematically represented 
behind the man and the woman. A civilization that acquires the plaque will, of 
course, also acquire the spacecraft, and will be able to determine that the distance 
indicated is indeed close to 8 times 21 centimeters, thus confirming that the 
symbol at top left represents the hydrogen hyperfine transition. 

Further binary numbers are shown in the radial pattern comprising the main 
part of the diagram at left center. These numbers, if written in decimal notation, 
would be ten digits long. They must represent either distances or times. If 
distances, they are of the order of several times 10 11 centimeters, or a few dozen 
times the distance between the Earth and the Moon. It is highly unlikely that we 
would consider them useful to communicate. Because of the motion of objects 
within the Solar System, such distances vary in continuous and complex ways. 

However, the corresponding times are on the order of 1/10 second to 1 second. 
These are the characteristic periods of the pulsars, natural and regular sources of 
cosmic radio emission; pulsars are rapidly rotating neutron stars produced in 
catastrophic stellar explosions (see Chapter 38). We believe that a scientifically 
sophisticated civilization will have no difficulty understanding the radial burst 
pattern as the positions and periods of 14 pulsars with respect to the Solar System 
of launch. 

But pulsars are cosmic clocks that are running down at largely known rates. 
The recipients of the message must ask themselves not only where it was ever 
possible to see 14 pulsars arrayed in such a relative position, but also when it was 
possible to see them. The answers are: Only from a very small volume of the 
Milky Way Galaxy and in a single year in the history of the Galaxy. Within that 
small volume there are perhaps a thousand stars; only one is anticipated to have 
the array of planets with relative distances as indicated at the bottom of the 
diagram. The rough sizes of the planets and the rings of Saturn are also 
schematically shown. A schematic representation of the initial trajectory of the 


spacecraft launched from Earth and passing by Jupiter is also displayed. Thus, the 
message specifies one star in about 250 billion and one year (1970) in about 10 

The content of the message to this point should be clear to an advanced 
extraterrestrial civilization, which will, of course, have the entire Pioneer 10 
spacecraft to examine as well. The message is probably less clear to the man on 
the street, if the street is on the planet Earth. (However, scientific communities on 
Earth have had little difficulty decoding the message.) The opposite is the case 
with the representations of human beings to the right. Extraterrestrial beings, 
which are the product of 4.5 billion years or more of independent biological 
evolution, may not at all resemble humans, nor may the perspective and line- 
drawing conventions be the same there as here. The human beings are the most 
mysterious part of the message. 


4. A Message to Earth 

The golden greeting card placed aboard the Pioneer io spacecraft was intended for 
the remote contingency that representatives of an advanced extraterrestrial 
civilization, some time in the distant future, might encounter this first artifact of 
mankind to leave the Solar System. But the message has had a more immediate 
impact. It has already been meticulously studied — not by extraterrestrials, but by 
terrestrials. Human beings all over the planet Earth have examined the message, 
applauded it, criticized it, interpreted it, and proposed alternative messages. 

The graphics of the message have been reproduced widely in newspapers and 
television programs, small art and literary magazines, and national newsweeklies. 
We have received letters from scientists and housewives, historians and artists, 
feminists and homosexuals, military and foreign service officers, and one professor 
of bass fiddle. Our plaque has been reproduced for commercial sale by an 
engraving company, a distributor of scientific knickknacks, a manufacturer of 
tapestry, and an Italian mint specializing in silver ingots - all, incidentally, without 

The great majority of comments have been favorable, some extraordinarily 
enthusiastic. The large street advertising billboards for the Tribune of Geneva, 
Switzerland, announced " Message de la NASA pour les extraterrestresV' One 
scientist writes to say that the description of the scientific basis of the plaque we 
published in the American journal Science was the first scientific paper he had 
ever read that moved him to tears of joy. A correspondent in Athens, Georgia, 
writes, "We'll all be gone before this particular message in a bottle is picked up by 
some indescribable spacecomber; nevertheless, its very existence, the audacity of 
the dream, inevitably produces in me - and many others I know — the feelings of a 
Balboa, a Leeuwenhoek, a human being being human!" 

At the California Institute of Technology, where the graffiti is arcane, some 
unknown artist drew the message life-size on a barrier at a building site, eliciting 
friendly greetings from the inhabitants, which we hope will serve as a model for 
extraterrestrial readers (see the illustration on the facing page) . 


Graffiti at Caltech: A response to the Pioneer 10 plaque. 

Courtesy "Engineering and Science," California Institute ot 
Technology, Pasadena, Calif. 

But there were also critical comments. They were not directed at the pulsar 
map, which was the scientific heart of the message, but rather at the 
representation of the man and the woman. The original drawings of this couple 
were made by my wife and were based upon the classical models of Greek 
sculpture and the drawings of Leonardo da V inci. We do not think this man and 
woman are ignoring each other. They are not shown holding hands lest the 
extraterrestrial recipients believe that the couple is one organism joined at the 
fingertips. (In the absence of indigenous horses, both the Aztecs and the Incas 
interpreted the mounted conquistador as one animal - a kind of two-headed 
centaur.) The man and woman are not shown in precisely the same position or 
carriage so that the suppleness of the limbs could be communicated - although we 


well understand that the conventions of perspective and line drawing popular on 
Earth may not be readily apparent to civilizations with other artistic conventions. 

The man's right hand is raised in what I once read in an anthropology book is a 
"universal" sign of good will - although any literal universality is of course unlikely. 
At least the greeting displays our opposable thumbs. Only one of the two people 
is shown with hand raised in greeting, lest the recipients deduce erroneously that 
one of our arms is bent permanently at the elbow. 

Several women correspondents complain that the woman appears too passive. 
One writes that she also wishes to greet the universe, with both arms outstretched 
in womanly salutation. The principal feminine criticism is that the woman is 
drawn incomplete - that is, without any hint of external genitalia. The decision to 
omit a very short line in this diagram was made partly because conventional 
representation in Greek statuary omits it. But there was another reason: Our desire 
to see the message successfully launched on Pioneer io. In retrospect, we may have 
judged NASA's scientific-political hierarchy as more puritanical than it is. In the 
many discussions that I held with such officials, up to the Administrator of the 
National Aeronautics and Space Administration and the President's Science 
Adviser, not one V ictorian demurrer was ever voiced; and a great deal of helpful 
encouragement was given. 

Y et it is clear that at least some individuals were offended even by the existing 
representation. The Chicago Sun Times, for example, published three versions of 
the plaque in different editions all on the same day: In the first the man was 
represented whole; in the second, suffering from an awkward and botched 
airbrush castration; and in the final version - intended no doubt to reassure the 
family man dashing home - with no sexual apparatus at all. This may have pleased 
one feminist correspondent who wrote to the New York Times that she was so 
enraged at the incomplete representation of the woman that she had an irresistible 
urge "to cut off the man's . . . right arm!" 

The Philadelphia Inquirer published on its front page an illustration of the 
plaque, but with the nipples of the woman and the genitalia of the man removed. 
The assistant managing editor was quoted as saying, "A family newspaper must 
uphold community standards." 

An entire mythology has evolved about the absence of discernible female 
genitalia. It was a column by the respected science writer Tom O'Toole, of the 
Washington Post, that first reported that NASA officials had censored an original 
depiction of the woman. This tale was then circulated in nationally syndicated 
columns by Art Hoppe, Jack Stapleton, Jr., and others. Stapleton imagined the 
enraged citizens of another planet receiving the plaque, and in a paroxysm of 
moral outrage covering over with adhesive tape the pornographic representation 
of the feet of the man and the woman. One letter writer to the Washington Daily 
News proposed that if the woman was to be censored, then for consistency the 
noses of the humans should have been painted blue. A tut-tutting letter in Playboy 
magazine complained about this further intrusion of government censorship, 


already quite bad enough, into the lives of the citizenry. Editorials in science- 
fiction magazines also took the government to task. The idea of government 
censorship of the Pioneer io plaque is now so well documented and firmly 
entrenched that no statement from the designers of the plaque to the contrary can 
play any role in influencing the prevailing opinion. But we can at least try. 

What sexuality there is in the message also drew epistolary fire. The Los 
Angeles Times published a letter from an irate reader that went: 

I must say I was shocked by the blatant display of both male and female sex 
organs on the front page of the Times. Surely this type of sexual exploitation 
is below the standards our community has come to expect from the Times. 

Isn't it enough that we must tolerate the bombardment of pornography 
through the media of film and smut magazines? Isn't it bad enough that our 
own space agency officials have found it necessary to spread this filth even 
beyond our own solar system? 

This was followed several days later by another letter in the Times: 

I certainly agree with those people who are protesting our sending those 
dirty pictures of naked people out into space. I think the way it should have 
been done would have been to visually bleep out the reproductive organs of 
the drawings of the man and the woman. Next to them should have been a 
picture of a stork carrying a little bundle from heaven. 

Then if we really want our celestial neighbors to know how far we have 
progressed intellectually, we should have included pictures of Santa Claus, 
the Easter Bunny, and the Tooth Fairy. 

The New York Daily News headlined the story in typical fashion: "Nudes and 
Map tell about Earth to Other Worlds." 

Some correspondents argue that the function of the sexual organs would not be 
obvious even had they been graphically displayed, and urged on us a sequence of 
cartoons from copulation to birth to puberty to copulation. There was not quite 
room for this on a 6-inch by g-inch plaque. I can also imagine the letters that 
would then have been written to the Los Angeles Times. 

An article in Catholic Review criticizes the plaque because it "includes 
everything but God," and suggests that, rather than a pair of human beings, it 
would have been better to have borne a sketch of a pair of praying hands. 

Another correspondent maintains that the perspective conventions are 
insuperably difficult, and urges us to send the complete cadavers of a man and a 
woman. They would be perfectly preserved in the cold of space, and could be 
examined by extraterrestrials in detail. We declined on grounds of excess weight. 

The front page of the Berkeley, California, Barb, apparently intending to 
convey an impression that the man and woman on the message were too straight, 
reproduced them with the caption, "Hello. We're from Orange County." 

This comment touches on an aspect of the representation of the man and 
woman that I personally feel much worse about, although it has received almost 
no other public notice. In the original sketches from which the engravings were 
made, we made a conscious attempt to have the man and woman panracial. The 


woman was given epicanthian folds and in other ways a partially Asian 
appearance. The man was given a broad nose, thick lips, and a short "Afro" haircut. 
Caucasian features were also present in both. We had hoped to represent at least 
three of the major races of mankind. The epicanthian folds, the lips, and the nose 
have survived into the final engraving. But because the woman's hair is drawn only 
in outline, it appears to many viewers as blond, thereby destroying the possibility 
of a significant contribution from an Asian gene pool. Also, somewhere in the 
transcription from the original sketch drawing to the final engraving the Afro was 
transmuted into a very non- African Mediterranean-curly haircut. Nevertheless, the 
man and woman on the plaque are, to a significant degree, representative of the 
sexes and races of mankind. 

Professor E. Gombrich, the Director of the Warburg Institute, a leading art 
school in London, criticizes the plaque in the journal Scientific American. He 
wonders how the plaque can possibly be expected to be visible to an 
extraterrestrial organism that may not have developed the sense of sight at visible 
wavelengths. The answer is derived simply from the laws of physics. Planetary 
atmospheres absorb light from the nearby sun or suns because of three molecular 
processes. The first is a change in the energy state of individual electrons attached 
to atoms. These transitions occur in the ultraviolet, X-ray, and gamma-ray parts of 
the spectrum and tend to make a planetary atmosphere opaque at these 
wavelengths. Second, there are vibrational transitions that occur when two atoms 
in a given molecule oscillate with respect to each other. Such transitions tend to 
make planetary atmospheres opaque in the near infrared part of the spectrum. 
Third, molecules undergo rotational transitions, due to the free rotation of the 
molecule. Such transitions tend to absorb in the far infrared. As a result, quite 
generally, the radiation from the nearby star, which penetrates through a planetary 
atmosphere, will be in the visible and in the radio parts of the spectrum - the 
parts that are not absorbed by the atmosphere. 

In fact, these are the principal "windows" that astronomers use for surveying 
the universe from the Earth's surface. But radio wavelengths are so long that no 
organisms of reasonable size can develop pictures of their surroundings with radio 
wavelength "eyes." Therefore, we expect optical frequency sensors to be 
developed quite widely among organisms on planets of stars throughout the 

However, even if we imagine organisms whose eyes work in the infrared region 
(or, for that matter, in the gamma-ray region) and who are able to intercept 
Pioneer io in interstellar space, it is probably not asking too much of them to have 
contrivances that scan the plaque at frequencies to which their eyes are insensitive. 
Because the engraved lines on the plaque are darker than the surrounding gold- 
anodized aluminum, the message should be entirely visible even in the infrared. 

Gombritch also takes us to task for portraying an arrow as a sign of the 
spacecraft's trajectory. He maintains that arrows would be understandable only to 
civilizations that have evolved, as ours has, from a hunting society. But here again 


it does not take a very intelligent extraterrestrial to understand the meaning of the 
arrow. There is a line that begins on the third planet of a solar system and ends, 
somewhere in interstellar space, at a schematic representation of the spacecraft - 
which the discoverers of the message have at "hand": The plaque is attached to the 
spacecraft From this I would hope they would be able to argue backward to our 
hunter- gatherer ancestors. 

In the same way, the relative distances of the planets from the Sun, shown by 
binary notation at the bottom of the plaque, indicate that we use base-io 
arithmetic. From the fact that we have 10 fingers and 10 toes - drawn with some 
care on the plaque - I hope any extraterrestrial recipients will be able to deduce 
that we use base-io arithmetic and that some of us count on our fingers. From the 
stumpiness of our toes they may even be able to deduce that we evolved from 
arboreal ancestors. 

There are other respects in which the message has proved to be a psychological 
projective test. One man writes of his concern that the message has doomed all of 
mankind. American movies of Second World War vintage, he argues, are very 
likely propagating via television transmission through interstellar space. From such 
programming, the extraterrestrials will easily be able to deduce (1) that the Nazis 
were very bad fellows, and (2) that they greeted each other with their right hand 
extended outward. From the fact that the man on the plaque is portrayed as 
making what our correspondent erroneously perceives as the same sort of greeting, 
he is concerned that the extraterrestrials will deduce that the wrong side won 
World War II and promptly mount a punitive expedition to Earth to set matters 

Such a letter more nearly describes the state of mind of the writer than of the 
likely extraterrestrial recipients of the message. The raised right hand in greeting is 
historically connected with militarism, but in a negative way: The raised and 
empty right hand symbolizes that no weapon is being carried. 

For me, some of the most moving responses to the message are the works of 
art and poetry that it evoked. Mr. 'Aim Morhardt is a painter of water colors of 
the desert and sierras who lives in Bishop, California, where, perhaps not 
coincidentally, the giant Goldstone tracking station, which commands Pioneer 10, is 
located. Mr. Morhardt's poem follows: 

Pioneer 10: The Golden Messenger. 

The dragon prows that cruised the northern seas, 

Questing adventure with the fighting clan; 

The gallant mermaid bows blown down the breeze 
On barquentine and slim-hulled merchantman; 

All the discoverers of unknown lands 

Gone in this winged age where naught remains 

Of new strange treasure on some foreign strand, 

So well-known earth, such charted routes and lanes. 

Now the new figurehead of man appears, 

Facing the vast immeasurable unknown, 


Naked, star-sped, beyond the call of years, 

Hand in hand, outward bound, and so alone. 

Go, tiny messenger of our your race, 

Touch, if you can, harbor in some far place. 

Mr. Arvid F. Sponberg, of Belfast, Northern Ireland, writes: "The voyage of 
Pioneer 10 — and the voyages of those like her - will have an effect that poets, 
painters and musicians will not long ignore. The existence of the idea of Pioneer io 
is proof of this. The scientific mission of course is of incalculable value and 
interest, but the idea of the journey is of even greater imaginative value. Pioneer io 
brings closer the day when artists must confront man's new voyage as experience 
and not fantasy." 

Mr. Sponberg composed for us a poem in sonnet form: 

New Odyssey 

Away, afar, beyond, bereft of kin, 

Wayward, wandering, far ranging vagabonds, 

Yearning, stardrawn, the Pioneers sweep on, 

Outward bound, adrift on the solar wind. 

A man, a woman, orphans of warm earth 
Or splendid voyageurs with golden sails, 

Or gypsies roaming ancient stellar trails, 

A caravan in quest of celestial berth. 

If, deep within cold interstellar space, 

Some fearful eye spies life on this raft, 

Will it perceive the heart within our craft, 

A pulsar pounding out the rhythms of peace? 

A spirit's starburst pierces new frontiers; 

An Odyssey is our home; let us praise Pioneers! 

There is, of course, the possibility that the message on Pioneer io — invented by 
human beings but directed at creatures of a very different kind - may prove 
ultimately mysterious to them. We think not. We think we have written the 
message - except for the man and woman — in a universal language. The 
extraterrestrials cannot possibly understand English or Russian or Chinese or 
Esperanto, but they must share with us common mathematics and physics and 
astronomy. I believe that they will understand, with no very great effort, this 
message written in the galactic language: "Scientific." 

But we may be wrong. One exploration of a total misunderstanding - and by 
far the most amusing such description - was made by the British humor magazine 
Punch in an article headlined, "According to the [Paris] Herald Tribune only one in 
ten of NASA scientists was able to figure out its message. So what chance have 
the aliens got?" Punch presents an opinion sampling of four representative 
extraterrestrials. They should be read with close reference to the illustration of the 
actual message: 

"Still, I must emphasise that we are only guessing at this stage and none of us 
has been able to explain the significance of the dots along the bottom. A 


suggestion that it could be a map of some metropolitan railway has been made to 
us, but we feel that this fails to take into account the arrowed position of a 
capsized yacht, or possibly a garden trowel. The inclusion of a naked blonde makes 
it more than likely, however, that this is some kind of a joke sent out by a 
backward planet, possibly that being used by the Earthlings." 

"Speaking as a fourteen-legged and extremely thin spider," said a voice from 
the back of Andromeda 9, "I have studied this post-card from the Earthlings and I 
take it as a snub. The caricature of our species is both crude and inept, suggesting, 
amongst other things, that we've got a right leg longer than all the rest. 
Furthermore, the geometric being which is standing at the back has clearly turned 
its back on us and one of the other two is pointing five antennae in a frankly 
sordid gesture. There seems little reason to doubt, amongst us intelligent spiders, 
that this thing is intended as a declaration of war. The illustrated talent for the 
creature on the right to be capable of firing arrows from the shoulder is a 
particularly sinister turn and one that bodes badly for a long and bitter struggle 
with the Earthlings." 

"Whatever it is," the Being declared, "it's not come all this way for nothing. My 
guess is that it's trying to tell us something. Just suppose, for argument's sake, that 
this thing which we have before us is not an actual creature itself but an artifact of 
some sort. Such a theory might explain for a start why it hasn't so far uttered in 
any way. No, this thing was sent - probably from some primitive three- 
dimensional world — and I say it's meant to be a picture or a cipher with a message 
for us Beings. What the message is, of course, depends on which way up it's 
supposed to be. I shouldn't be a bit surprised if it was rude." 

"Magnificent!" The thing on Alpha Centaurus was overcome with awe. "Truly 
magnificent! As far as is known, this is the first time ever that has fetched up on 
our planet an original work by the erstwhile Earthling Leonardo da Vinci! Our 
telescopes show that the style is unmistakably his. Nevertheless, the discovery is 
bound to alter some of the intelligence data on the Earth. It was not known, until 
now, that the climate was sufficiently warm for policemen to go to point duty 
without clothes in their world nor that key limbs on the Earthlings are apparently 
operated by string. Let us hope they send us further simple greeting-cards soon." 

Perhaps the most perceptive editorial comment is the New York Times': 

. . . that gold-plated plaque is more of a challenge to us. Despite the uncanny 
mastery of celestial laws that permits man to shoot his artifacts at the stars, 
we find ourselves still depressingly inept at ordering our own systems here 
on Earth. Even as we try to find a way to insure that sapient man will not 
consume his planet in nuclear fires, a rising chorus warns us that man may 
very well exhaust his earth either by overbreeding or by inordinate demands 
on its resources, or both. 

So the marker launched into space is at the same time a gauntlet thrown 
down to earth: That the gold-plated plaque convey in its time the message 
that man is still here — not that he had been here. 


The message aboard Pioneer io has been good fun. But it has been more than 
that. It is a kind of cosmic Rorschach test, in which many people see reflected 
their hopes and fears, their aspirations and defeats - the darkest and the most 
luminous aspects of the human spirit. 

The sending of such a message forces us to consider how we wish to be 
represented in a cosmic discourse. What is the image of mankind that we might 
wish to represent to a superior civilization elsewhere in the Galaxy? The 
transmittal of the Pioneer io message encourages us to consider ourselves in cosmic 

The greater significance of the Pioneer io plaque is not as a message to out 
there; it is as a message to back here. 



5- Experiments in Utopias 

In assessing the likelihood of advanced technical civilizations elsewhere in the 
Galaxy, the most important fact is the one about which we know least — the 
lifetime of such a civilization. If civilizations destroy themselves rapidly after 
reaching the technological phase, at any given moment (like now) there may be 
very few of them for us to contact. If, on the other hand, a small fraction of 
civilizations learn to live with weapons of mass destruction and avoid both natural 
and self- generated catastrophes, the number of civilizations for us to communicate 
with at any given moment may be very large. 

This assessment is one reason we are concerned about the lifetime of such 
civilizations. There is a more pressing reason, of course. For personal reasons, we 
hope that the lifetime of our own civilization will be long. 

There is probably no epoch in the history of mankind that has undergone so 
much and so many varieties of change as the present time. Two hundred years ago, 
information could be sent from one city to another no faster than by horse. Today, 
the information can be sent via telephone, telegraph, radio, or television at the 
velocity of light. In two hundred years the speed of communication has increased 
by a factor of thirty million. We believe there will be no corresponding future 
advance, since messages cannot, we believe, be sent faster than the velocity of 

Two hundred years ago it took as long to go from Liverpool to London as it 
now does from the Earth to the Moon. Similar changes have occurred in the 
energy resources available to our civilization, in the amount of information that is 
stored and processed, in methods of food production and distribution, in the 
synthesis of new materials, in the concentration of population from the 
countryside to the cities, in the vast increase in population, in improved medical 
practice, and in enormous social upheaval. 

Our instincts and emotions are those of our hunter-gatherer ancestors of a 
million years ago. But our society is astonishingly different from that of a million 
years ago. In times of slow change, the insights and skills learned by one generation 
are useful, tried, and adaptive, and are gladly received when passed down to the 
next generation. But in times like today, when the society changes significantly in 
less than a human lifetime, the parental insights no longer have unquestioned 
validity for the young. The so-called generation gap is a consequence of the rate of 
social and technological change. 

Even within a human lifetime, the change is so great that many people are 
alienated from their own society. Margaret Mead has described older people today 
as involuntary immigrants from the past to the present. 

Old economic assumptions, old methods of determining political leaders, old 
methods of distributing resources, old methods of communicating information 
from the government to the people - and vice versa — all of these may once have 
been valid or useful or at least somewhat adaptive, but today may no longer have 


survival value at all. Old oppressive and chauvinistic attitudes among the races, 
between the sexes, and between economic groups are being justifiably challenged. 
The fabric of society throughout the world is ripping. 

At the same time, there are vested interests opposed to change. These include 
individuals in power who have much to gain in the short run by maintaining the 
old ways, even if their children have much to lose in the long run. They are 
individuals who are unable in middle years to change the attitudes inculcated in 
their youth. 

The situation is a very difficult one. The rate of change cannot continue 
indefinitely; as the example of the rate of communication indicates, limits must be 
reached. We cannot communicate faster than the velocity of light. We cannot 
have a population larger than Earth's resources and economic distribution facilities 
can maintain. Whatever the solutions to be achieved, hundreds of years from now 
the Earth is unlikely still to be experiencing great social stress and change. We will 
have reached some solution to our present problems. The question is, which 

In science a situation as complicated as this is difficult to treat theoretically. 
We do not understand all the factors that influence our society and, therefore, 
cannot make reliable predictions on what changes are desirable. There are too 
many complex interactions. Ecology has been called the subversive science 
because every time a serious effort to preserve a feature of the environment is 
made, it runs into enormous numbers of social or economic vested interests. The 
same is true every time we attempt to make a major change in anything that is 
wrong; the change runs through society as a whole. It is difficult to isolate small 
fragments of the society and change them without having profound influences on 
the rest of society. 

When theory is not adequate in science, the only realistic approach is 
experimental. Experiment is the touchstone of science on which the theories are 
framed. It is the court of last resort. What is clearly needed are experimental 

There is good biological precedent for this idea. In the evolution of life there 
are innumerable cases when an organism was clearly dominant, highly specialized, 
perfectly acclimatized to its environment. But the environment changed and the 
organism died. It is for this reason that nature employs mutations. The vast 
majority of mutations are deleterious or lethal. The mutated species are less 
adaptive than the normal types. But one in a thousand or one in ten thousand 
mutants has a slight advantage over its parents. The mutations breed true, and the 
mutant organism is now slightly better adapted. 

Social mutations, it seems to me, are what we need. Perhaps because of a hoary 
science-fiction tradition that mutants are ugly and hateful, it might be better to 
use another term. But social mutation - a variation on a social system which 
breeds true, which, if it works, is the path to the future - seems to be precisely 


the right phrase. It would be useful to examine why some of us find the phrase 

We should be encouraging social, economic, and political experimentation on a 
massive scale in all countries. Instead, the opposite seems to be occurring. In 
countries such as the United States and the Soviet Union the official policy is to 
discourage significant experimentation, because it is, of course, unpopular with the 
majority. The practical consequence is vigorous popular disapproval of significant 
variation. Young urban idealists immersed in a drug culture, with dress styles 
considered bizarre by conventional standards, and with no prior knowledge of 
agriculture, are unlikely to succeed in establishing Utopian agricultural 
communities in the American Southwest - even without local harassment. Yet 
such experimental communities throughout the world have been subjected to 
hostility and violence by their more conventional neighbors. In some cases the 
vigilantes are enraged because they themselves have only within the previous 
generation been accepted into the conventional system. 

We should not be surprised, then, if experimental communities fail. Only a 
small fraction of mutations succeed. But the advantage social mutations have over 
biological mutations is that individuals learn; the participants in unsuccessful 
communal experiments are able to assess the reasons for failure and can 
participate in later experiments that attempt to avoid the causes of initial failure. 

There should be not only popular approval for such experiments, but also 
official governmental support for them. Volunteers for such experiments in 
Utopia - facing long odds for the benefit of society as a whole — will, I hope, be 
thought of as men and women of exemplary courage. They are the cutting edge of 
the future. One day there will arise an experimental community that works much 
more efficiently than the polyglot, rubbery, hand-patched society we are living in. 
A viable alternative will then be before us. 

I do not believe that anyone alive today is wise enough to know what such a 
future society will be like. There may be many different alternatives, each 
potentially more successful than the pitifully small variety that face us today. 

A related problem is that the non- Western, non-technological societies, 
viewing the power and great material wealth of the West, are making great strides 
to emulate us - in the course of which many ancient traditions, world-views, and 
ways of life are being abandoned. For all we know, some of the alternatives being 
abandoned contain elements of precisely the alternatives we are seeking. There 
must be some way to preserve the adaptive elements of our societies - painfully 
worked out through thousands of years of sociological evolution - while at the 
same time coming to grips with modern technology. The principal immediate 
problem is to spread the technological achievements while maintaining cultural 

An opinion sometimes encountered is that the problem is technology itself. I 
maintain that it is the misuse of technology by the elected or self-appointed 
leaders of societies, and not technology itself, that is at fault. W ere we to return to 


more primitive agricultural endeavors, as some have urged, and abandon modern 
agricultural technology, we would be condemning hundreds of millions of people 
to death. There is no escape from technology on our planet. The problem is to use 
it wisely. 

For quite similar reasons, technology must be a major factor in planetary 
societies older than ours. I think it likely that societies that are immensely wiser 
and more benign than ours are, nevertheless, more highly technological than we. 

W e are at an epochal, transitional moment in the history of life on Earth. There 
is no other time as risky, but no other time as promising for the future of life on 
our planet. 


nc »eiu vtont uat^cxurw •» t# mt€ on 

A comment on chauvinism. Courtesy, Paul Conrad, Los Ange- 
les Timesr. 


6. Chauvinism 

Jokes are a way of dealing with anxiety. There is a class of jokes dealing with 
extraterrestrial life. In one, the extraterrestrial visitor lands on Earth, walks up to a 
gasoline pump or a gumball machine — the accounts differ - and asks, "What's a 
nice girl like you doing in a place like this?" 

Elsewhere, beings are doubtless very different from us. But the joke assumes 
that extraterrestrial organisms will be, if not like human beings, then like gasoline 
pumps or gumball machines. The most likely circumstance is that extraterrestrial 
beings will look nothing like any organisms or machines familiar to us. 
Extraterrestrials will be the product of billions of years of independent biological 
evolution, by small steps, each involving a series of tiny mutational accidents, on 
planets with very different environments from those that characterize Earth. 

But such jokes underscore a general problem and a general virtue in thinking 
about life elsewhere. The problem is that we have only one kind of life to study, 
the co-related biology of the planet Earth, all organisms of which have descended 
from a single instance of the origin of life. It is difficult for the biologist, as well as 
the layman, to determine what properties of life on our planet are accidents of the 
evolutionary process and what properties are characteristic of life everywhere. The 
assumption that life elsewhere has to be, in some major sense, like life here is a 
conceit I will call chauvinism. 

While such chauvinism has been common throughout human history, clearer 
views have occasionally surfaced, for example, by the great French astronomer 
Pierre Simon, the Marquis de Leplace. In his classic work La Mecanique Celeste he 
wrote: " [The Sun's] influence gives birth to the animals and plants which cover the 
surface of the Earth, and analogy induces us to believe that it produces similar 
effects on the planets; for it is not natural to pose that matter, of which we see the 
fecundity develop itself in such various ways, should be sterile upon a planet so 
large as Jupiter, which, like the Earth, has its days, its nights, and its years, and on 
which observation discovers changes that indicate very active forces. Man, formed 
for the temperature which he enjoys upon the Earth, could not, according to all 
appearance, live upon the other planets; but ought there not to be a diversity of 
organization suited to the various temperatures of the globes of this universe? If 
the difference of elements and climates alone causes such variety in the 
production of the Earth, how infinitely diversified must be the production of the 
planets and their satellites?" Laplace wrote these words near the end of the 
eighteenth century. 

The virtue of thinking about life elsewhere is that it forces us to stretch our 
imaginations. Can we think of alternative solutions to biological problems already 
solved in one particular way on Earth? For example, the wheel is a comparatively 
recent invention on the planet Earth. It seems to have been invented in the ancient 
Near East less than ten thousand years ago. In fact, the high civilizations of Meso- 
America, the Aztecs and the Mayas, never employed the wheel, except for 


children's toys. Biology — the evolutionary process - has never invented the wheel, 
in spite of the fact that its selective advantages are manifest. Why are there no 
wheeled spiders or goats or elephants rolling along the highways? The answer is 
clearly that, until recently, there were no highways. Wheels are of use only when 
there are surfaces to roll on. Since the planet Earth is a heterogeneous, bumpy 
place with few long, smooth areas, there was no advantage to evolving the wheel. 
We can very well imagine another planet with enormous long stretches of smooth 
lava fields in which wheeled organisms are abundant. The late Dutch artist M. C. 
Escher designed a salamander-like organism that would do very well in such an 

The evolution of life on Earth is a product of random events, chance 
mutations, and individually unlikely steps; small differences early in the evolution 
of life have a profound significance later in the evolution of life. W ere we to start 
the Earth over again and let only random factors operate, I believe that we would 
wind up with nothing at all resembling human beings. This being the case, how 
much less likely it is that organisms evolving over five billion or more years, 
independently in a quite different environment of another planet of a far-off star, 
would closely resemble human beings. 

Thus, the hoary science-fiction standby of the sexual love between a human 
being and an inhabitant of another planet ignores, in the most fundamental sense, 
the biological realities. John Carter could love Dejah Thoris, but, despite what 
Edgar Rice Burroughs believed, their love could not be consummated. And if it 
could, a viable offspring would not be possible. Likewise, the category of contact 
story, now quite fashionable in some UFO enthusiast circles, of sexual contact 
between human and saucerian - most recently described in a weekly newspaper 
headline with the modest title "We Sexed a Blonde from a Flying Saucer!" - must 
be relegated to the realm of improbable fantasy. Such crossings are about as 
reasonable as the mating of a man and a petunia. 

A popular phrase — often encountered in popular books on the planets - is "life 
as we know it." We read that "life as we know it" is impossible on this planet or 
that. But what is life as we know it? It depends entirely on who the "we" is. A 
person who is unsophisticated in biology, who lacks a keen appreciation of the 
multitudinous adaptations and varieties of terrestrial organisms, will have a meager 
idea of the range of possible biological habitats. There are discussions, even by 
famous scientists, that give the impression that an environment that is 
uncomfortable for my grandmother is impossible for life. 

At one time it was thought that oxides of nitrogen had been detected in the 
atmosphere of Mars. A scientific paper was published on this apparent finding. 
The authors of the paper argued that life on Mars was, therefore, impossible, 
because oxides of nitrogen are poisonous gases. There are at least two objections 
to this argument. First, oxides of nitrogen are poisonous gases only to some 
organisms on Earth. Second, what quantity of oxides of nitrogen were thought to 
be discovered on Mars? When I calculated the amount, it turned out to be less 


than the average abundance above Los Angeles. The oxides of nitrogen are an 
important constituent of smog. Life in Los Angeles may be difficult, but it is not 
yet impossible. The same conclusion applies to Mars. The final problem with 
these particular observations is that they are very likely mistaken; later studies - 
for example, observations Tobias Owen and I made with the Orbiting 
Astronomical Observatory - have shown no oxides of nitrogen in the atmosphere 
of Mars. 

Oxygen chauvinism is common. If a planet has no oxygen, it is alleged to be 
uninhabitable. This view ignores the fact that life arose on Earth in the absence of 
oxygen. In fact, oxygen chauvinism, if accepted, logically demonstrates that life 
anywhere is impossible. Fundamentally, oxygen is a poisonous gas. It chemically 
combines with and destroys the organic molecules of which terrestrial life is 
composed. There are many organisms on Earth that do without oxygen and many 
organisms that are poisoned by it. 

All of the earliest organisms on Earth did not use molecular oxygen, 0 2 . In a 
brilliant set of evolutionary adaptations, organisms like insects and frogs and fish 
and people learned not only to survive in the presence of this poisonous gas but 
actually to use it to increase the efficiency with which we metabolize foodstuffs. 
But that should not blind us to the fundamentally poisonous character of this gas. 
The absence of oxygen on a place such as Jupiter is, therefore, hardly an argument 
against life on such planets. 

There are ultraviolet light chauvinists. Because of the oxygen in the Earth's 
atmosphere, a variety of oxygen molecule called ozone (Oj) is produced high in 
the atmosphere, about twenty-five miles above the surface. This ozone layer 
absorbs the middle-wavelength ultraviolet rays from the Sun, preventing them 
from reaching the surface of our planet. These rays are germicidal. They are 
emitted by ultraviolet lamps commonly used to sterilize surgical instruments. 
Strong ultraviolet rays from the Sun are an extremely serious hazard to most forms 
of life on Earth. But this is because most forms of life on Earth evolved in the 
absence of a high ultraviolet flux. 

It is easy to imagine adaptations to protect organisms against ultraviolet light. In 
fact, sunburn and high melanin pigmentation in the skin are adaptations in this 
direction. They have not been carried very far in most terrestrial organisms 
because the present ultraviolet flux is not very high. In a place like Mars, where 
there is little ozone, the ultraviolet light at the surface is extremely intense. But 
the Martian surface material is a strong absorber of ultraviolet light - as most soil 
and rocks are - and we can easily imagine organisms walking around with small 
ultraviolet-opaque shields on their backs: Martian turtles. Or perhaps Martian 
organisms carry about ultraviolet parasols. Many organic molecules also could be 
used in the exterior layers of extraterrestrial organisms to protect them against 
ultraviolet light. 

There are temperature chauvinists. It is said that the freezing temperatures on 
planets like Jupiter or Saturn, in the outer Solar System, make all life there 


impossible. But these low temperatures do not apply to all portions of the planet. 
They refer only to the outermost cloud layers — the layers that are accessible to 
infrared telescopes that can measure temperatures. Indeed, if we had such a 
telescope in the vicinity of Jupiter and pointed it at Earth, we would deduce very 
low temperatures on Earth: We would be measuring the temperatures in the 
upper clouds and not on the much warmer surface of Earth. 

It is now quite firmly established, both from theory and from radio 
observations of these planets, that as we penetrate below the visible clouds, the 
temperatures increase. There is always a region in the atmospheres of Jupiter, 
Saturn, Uranus, and Neptune that is at quite comfortable temperatures by 
terrestrial standards. 

But why is it necessary to have temperatures like those on Earth in order for 
life to proliferate? A human being is seriously inconvenienced if his body 
temperature is raised or lowered by a mere 20 degrees. Is this because we happen 
to live by accident on the one planet in the Solar System that has a surface at the 
right temperature for biology? Or is it that our chemistry is delicately attuned to 
the temperature of the planet on which we have evolved? The latter is almost 
surely the case. Other temperatures, other biochemistries. 

Our biological molecules are put together in complex three-dimensional 
arrangements. The functioning of these molecules, particularly the enzymes, are 
turned on and off by altering these three-dimensional arrangements. The chemical 
bonds that do these rearrangements must be weak enough to be broken 
conveniently at terrestrial temperatures, and at the same time strong enough not 
to fall to pieces if left alone for short periods of time. A chemical bond known as 
the hydrogen bond has an energy appropriately intermediate between these 
unreactive and unstable alternatives. The hydrogen bond is intimately connected 
with the three-dimensional biochemistry of terrestrial organisms. 

On a much hotter planet like Venus, our biological molecules would fall to 
pieces. On a much colder planet in the outer Solar System, our biological 
molecules would be rigid, and our chemical reactions would not proceed at any 
useful rate. However, it is conceivable that much stronger bonds on Venus and 
much weaker bonds in the outer Solar System play the same role that hydrogen 
bonds play on Earth. We may have been much too quick to reject life at 
temperatures very different from those on our planet. There are not many 
chemical reactions known that can proceed at useful rates at some very low 
temperature such as might exist on Pluto, 30 or 40 degrees above absolute zero. 
But there are also very few chemical laboratories on Earth where experiments are 
performed at 30 or 40 degrees above absolute zero. With a few exceptions, such 
experiments have not been performed at all. 

We are thus at the mercy of observational selection. We examine only a small 
fraction of the possible range of cases because of some unconscious bias, or the 
fact that scientists wish to work in their shirtsleeves. We then conclude that all 
conceivable cases must conform to what our preconceptions have forced upon us. 


Another common chauvinism - one which, try as I might, I find I share - is 
carbon chauvinism. A carbon chauvinist holds that biological systems elsewhere in 
the universe will be constructed out of carbon compounds, as is life on this planet. 
There are conceivable alternatives: Atoms like silicon or germanium can enter into 
some of the same kinds of chemical reactions as carbon does. It is also true that 
much more attention has been paid to carbon organic chemistry than to silicon or 
germanium organic chemistry, largely because most biochemists we know are of 
the carbon, rather than the silicon or germanium, variety. Nevertheless, from what 
we know of the alternative chemistries, it appears clear that — except in very low- 
temperature environments - there is a much wider variety of complex 
compounds that can be built from carbon than from the alternatives. 

In addition, the cosmic abundance of carbon exceeds that of silicon, 
germanium, or other alternatives. Everywhere in the universe, and particularly in 
primitive planetary environments in which the origin of life occurs, there is simply 
more carbon than alternative atoms available to make complex molecules. We see 
from laboratory experiments simulating the primitive atmosphere of the Earth or 
the present environment of Jupiter, as well as in radioastronomical studies of the 
interstellar medium, a profusion of simple and complex organic molecules readily 
produced by a wide variety of energy sources. For example, in one of our 
experiments, the passage of a single high-pressure shock wave through a mixture 
of methane (CEIJ, ethane (C 2 Hg), ammonia (NHj), and water (H 2 0) converted 38 
percent of the ammonia into amino acids, the building blocks of proteins. There 
were not enormous quantities of other sorts of organic molecules. 

Thus, both the atoms and the simple molecules of which we are made are 
probably common to organisms elsewhere in the universe. But the specific way in 
which these molecules are put together and the specific forms and physiologies of 
the extraterrestrial organisms may be, because of their different evolutionary 
histories, extremely different from what is common on our planet. 

In considering which stars to examine for possible radio signals directed at us, 
much attention is usually given to stars like our Sun. It has been reasonably argued 
that searches should begin with the one type of star we know has life on at least 
one of its planets, namely stars like our own Sun. In Project Ozma, the first 
attempt to search for such radio signals, the two stars examined, Tau Ceti and 
Epsilon Eridani, were both stars with mass, radius, age, and composition very 
similar to our Sun, which astronomers call a G-o dwarf. They were, in fact, the 
nearest two Sun-like stars. 

But should we restrict our attention to stars like the Sun? I think not. Stars of 
slightly smaller mass and of slightly lower luminosity than our Sun are longer lived. 
These stars, called K and M dwarfs, can be many billions of years older than the 
Sun. If we imagine that the longer the lifetime of a planet, the more likely it is that 
intelligent organisms have evolved on it, we should then bias our searches toward 
K and M stars and avoid G-star chauvinism. It may be objected that planets of K 
and M stars are much colder than Earth, and that life on them may be less likely. 


The premise of this objection does not appear to be true; such planets seem to be 
closer to their stars than the corresponding planets in our Solar System; and we 
have already discussed the fallacies of temperature chauvinism. Too, there are 
many more K and M stars than G stars. 

Is there planetary chauvinism? Must life arise and reside on planets, or might 
there be organisms that inhabit the depths of interstellar space, the surfaces or 
interiors of stars, or other even more exotic cosmic objects? 

In our present state of ignorance, these are very difficult questions to answer. 
The density of matter in interstellar space is so low that an organism there simply 
cannot acquire enough material to make a copy of itself in any reasonable period 
of time. This is not true in dense interstellar clouds, but such clouds live for very 
short periods of time, condensing to form stars and planets. In the process, they 
become so hot that any organic compounds contained within them are probably 

We might imagine organisms evolving on planets with atmospheres slowly 
leaking away to space, permitting the organisms gradually to adapt to the 
increasingly severe conditions, and finally acclimatizing to what in effect is an 
interstellar environment. Organisms leaving such planets - perhaps by 
electromagnetic radiation pressure, or by solar wind from the local sun - might 
populate interstellar space, but they would still be faced with insurmountable 
problems of malnutrition. 

A quite different sort of interstellar organism may be much more likely: 
Intelligent beings who arise on planets as we have, but who have moved their 
arena of activities to the much vaster volume of interstellar space. Beings in our far 
technological future should have capabilities at which we cannot today even dimly 
guess. It is not out of the question that such societies could tap the matter and 
energy of stars and galaxies for their own uses. Just as we are organisms completely 
at home only on the land, although we evolved from the sea, the universe may be 
populated with societies that arose on planets but that are comfortable only in the 
depths of interstellar space. 


Composer photograph by all-sky cameras of our Mflky Way 
Caluxv. Courtesy, Dr. Bart B«ik and Lund Observatory. 


7- Space Exploration as a Human Enterprise 

I. The Scientific Interest 

There is a place with four suns in the sky - red, white, blue, and yellow; two of 
them are so close together that they touch, and star-stuff flows between them. 

I know of a world with a million moons. 

I know of a sun the size of the Earth - and made of diamond. 

There are atomic nuclei a mile across that rotate thirty times a second. 

There are tiny grains between the stars, with the size and atomic composition 
of bacteria. 

There are stars leaving the Milky Way. There are immense gas clouds falling 
into the Milky Way. 

There are turbulent plasmas writhing with X- and gamma-rays and mighty 
stellar explosions. 

There are, perhaps, places outside our universe. 

The universe is vast and awesome, and for the first time we are becoming a 
part of it. 

The planets are no longer wandering lights in the evening sky. For centuries, 
Man lived in a universe that seemed safe and cozy — even tidy. Earth was the 
cynosure of creation and Man the pinnacle of mortal life. But these quaint and 
comforting notions have not stood the test of time. We now know that we live on 
a tiny clod of rock and metal, a planet smaller than some relatively minor features 
in the clouds of Jupiter and inconsiderable when compared with a modest 

Our star, the Sun, is small and cool and unprepossessing, one of some two 
hundred billion suns that make up the Milky Way Galaxy. We are located so far 
from the center of the Milky Way that it takes light, traveling at 186,000 miles a 
second, some 30,000 years to reach us from there. We are in the galactic 
boondocks, where the action isn't. The Milky Way Galaxy is entirely 
unremarkable, one of billions of other galaxies strewn through the vastness of 

No longer does "the world" mean "the universe." We live on one world among 
an immensity of others. 

Charles Darwin's insights into natural selection have shown that there are no 
evolutionary pathways leading unerringly from simple forms to Man; rather, 
evolution proceeds by fits and starts, and most life forms lead to evolutionary 
dead-ends. We are the products of a long series of biological accidents. In the 
cosmic perspective there is no reason to think that we are the first or the last or 
the best. 

These realizations of the Copernican and Darwinian revolutions are profound - 
and, to some, disturbing. But they bring with them compensatory insights. We 
realize our deep connectedness with other life forms, both simple and complex. 


We know that the atoms that make us up were synthesized in the interiors of 
previous generations of dying stars. We are aware of our deep connection, both in 
form and in matter, with the rest of the universe. The cosmos revealed to us by 
the new advances in astronomy and biology is far grander and more awesome than 
the tidy world of our ancestors. And we are becoming a part of it, the cosmos as it 
is, not the cosmos of our desires. 

Mankind now stands at several historical branching points. We are on the 
threshold of a preliminary reconnaissance of the cosmos. For the first time in his 
history, Man is capable of sending his instruments and himself from his home 
planet to explore the universe around him. 

But the exploration of space has been defended largely in terms of narrow 
considerations of national prestige, both in the United States and in the Soviet 
Union; in terms of the development of technological capabilities, in an age when 
many people are finding the development of technology for its own sake to have 
disastrous consequences; in terms of technological "spinoff when the space 
program costs very much more than the cost of direct development of the spinoff; 
and in terms of a quite tenuous argument for military advantage, in a time when 
people the world over long for a demilitarization of society. 

Under these circumstances, it is not surprising that hard questions are being 
asked about expenditures in space, when there are visible and urgent needs for 
funds to correct injustices and improve society and the quality of life on Earth. 
These questions are entirely appropriate. If scientists cannot give to the man on 
the street a satisfactory explanation of expenditures in the exploration of space, it 
is not obvious that public funds should be allocated for such ventures. 

The interest of an individual scientist in space exploration is likely to be very 
personal - something puzzles him, intrigues him, has implications that excite him. 
But we cannot ask the public to spend large sums just to satisfy the scientist's 
curiosity. When we probe more deeply into the professional interests of individual 
scientists, however, we often find a focus of concern that largely overlaps the 
public interest. 

A fundamental area of common interest is the problem of perspective. The 
exploration of space permits us to see our planet and ourselves in a new light. We 
are like linguists on an isolated island where only one language is spoken. We can 
construct general theories of language, but we have only one example to examine. 
It is unlikely that our understanding of language will have the generality that a 
mature science of human linguistics requires. 

There are many branches of science where our knowledge is similarly 
provincial and parochial, restricted to a single example among a vast multitude of 
possible cases. Only by examining the range of cases available elsewhere can a 
broad and general science be devised. 

The science that has by far the most to gain from planetary exploration is 
biology. In a very fundamental sense, biologists have been studying only one form 
of life on Earth. Despite the apparent diversity of terrestrial life forms, they are 


identical in the deepest sense. Beagles and begonias, bacteria and baleen whales all 
use nucleic acids for storage and transmission of hereditary information. They all 
use proteins for catalysis and control. All organisms on Earth, so far as we know, 
use the same genetic code. The cross-sectional structures of human sperm cells are 
almost identical with those of the cilia of paramecia. Chlorophyll and hemoglobin 
and the substances responsible for the coloring of many animals are all essentially 
the same molecule. 

It is difficult to escape the conclusion - which, in a sense, is implicit in 
Darwinian natural selection - that all life on Earth has evolved from a single 
instance of the origin of life. If this is true, there is an important sense in which the 
biologist cannot distinguish the necessary from the contingent, that is, distinguish 
those aspects of life that any organism anywhere in the universe must have simply 
in order to be alive, from those aspects of life that are the results of the tortuous 
evolution by small opportunistic adaptations. 

The production of simple organic (carbon-based) molecules under simulated 
primitive planetary conditions is now subject to active laboratory investigation. As 
we saw earlier, the molecules of which we are made can be produced rather easily, 
in the absence of life, under quite general primitive planetary conditions. But it is 
not practicable to perform laboratory experiments on even the early stages of 
biological evolution: The time scales are too long. It is only by examining living 
systems elsewhere that biologists can determine what other possibilities there are. 

It is for this reason that the discovery of even an extremely simple organism on 
Mars would have profound biological significance. On the other hand, if Mars 
proves to be lifeless, a natural experiment has been performed for us: Two planets, 
in many respects similar; but on one life has evolved, on the other it has not. By 
comparing the experimental with the control planet, much may be discovered 
about the origin of life. Similarly, the search for prebiological organic chemicals on 
the Moon, on Mars, or on Jupiter is of great importance in understanding the steps 
leading to the origin of life. 

As another example of the perspective provided by planetary studies, consider 
meteorology. The problems of turbulent flow and fluid dynamics are among the 
most difficult in all of physics. Some insights into the Earth's weather have been 
obtained by standing back and examining, by photography from meteorological 
satellites, the circulation of the Earth's atmosphere. Still, meteorological theory for 
the Earth is today capable of long-range weather predictions, but only over very 
large geographical areas, for a range of simplifying assumptions, and for only a little 
time into the future. Laboratory studies of atmospheric circulation have a limited 
scope; classically, they are performed in modified dishpans. 

It would be nice to do a "Joshua" experiment, stopping the Earth from turning 
for a while. The change in circulation would provide insights into the role of the 
Earth's rotation (particularly through Coriolis forces) in determining the 
circulation. But such an experiment is technologically very difficult. It also has 
undesirable side-effects. On the other hand, the planet Venus, with approximately 


the same mass and radius as Earth, has a rotation rate 240 times slower - so slow 
that Coriolis forces will be minor. The atmosphere is much thicker on Venus than 
on Earth. Nature has arranged a natural experiment for the meteorologists. 

Jupiter rotates about once every ten hours; here is an enormous planet that 
turns faster than Earth does. The effects of rotation should be much more 
important than on Earth, and, indeed, Jupiter gives the impression of having a 
seething, roiling, turbulent atmosphere; its prominent atmospheric bands and belts 
are almost certainly related to the rapid rotation. Nature has arranged two 
comparison experiments - two planets with massive atmospheres, one rotating 
slowly, the other rapidly. An understanding of the circulation of the massive 
atmospheres of Venus and Jupiter will improve our understanding of oceanic, as 
well as atmospheric, circulation on Earth. 

Or consider the planet Mars. Here is a planet with - quite remarkably - the 
same period of rotation and the same inclination of its axis of rotation to its orbital 
plane as Earth. But its atmosphere is only 1 percent of ours, and it has no oceans 
and no liquid water. Mars is a control experiment on the influence of oceans and 
liquid water on atmospheric circulation. 

Until recently, the geologist has been restricted to one object of study, the 
Earth. He was unable to decide which properties of the Earth are fundamental to 
all planetary surfaces and which are peculiar to the unique circumstances of Earth. 
For example, seismographic observations of earthquakes have revealed the interior 
structure of Earth and its division into crust, mantle, liquid metal core, and solid 
inner core. But the reason Earth is so divided remains largely obscure. Was Earth's 
crust exuded from the mantle through geological time? Did it fall from the skies in 
an early catastrophic event? Has Earth's core formed gradually through geological 
time by the sinking of iron through the mantle? Or did it form discontinuously, 
perhaps in a molten Earth at the time of the origin of our planet? Such questions 
can be examined by performing seismometric observations on the surfaces of 
other planets; they could be relatively inexpensive experiments performed 
automatically by existing instrumentation. 

There is now reasonably convincing evidence of continental drift. The motion 
of Africa and South America away from each other is the best-known example. In 
some theories, the driving force of continental drift and of the evolution of the 
interior of our planet are connected - for example, through convection currents 
circulating slowly between core and crust in the mantle. Such connections 
between surface geology and planetary interiors are just beginning to emerge in the 
study of other planets. We test our understanding of such connections by testing 
whether they apply elsewhere. 

The perspectives gained in studies like these have a range of practical 
consequences. A generalization of the science of meteorology may lead to great 
improvements in weather forecasting. It may even lead to weather modification. 
The study of the atmosphere of Venus has already led to the theory that a 
runaway "greenhouse" effect has occurred there - an unstable equilibrium in 


which an increase in temperature leads to an increase in the atmospheric water 
vapor content, leading through infrared absorption of thermal radiation from the 
planet to a yet further increase in surface temperature, and so on. Had Earth 
started out only slightly closer to the Sun than it did, preliminary theoretical 
estimates indicate that we might have ended up as a searing hot Venus. But we 
live in a time when the atmosphere of Earth is being strongly modified by the 
activities of Man. It is of the first importance to understand precisely what 
happened on Venus so that an accidental recapitulation on Earth of the runaway 
V enus greenhouse can be avoided. 

The studies of the surfaces and interiors of the planets may be of great practical 
benefit in earthquake prediction and in remote geological prospecting for minerals 
of value on Earth. 

The revolution in biology that the discovery of indigenous life elsewhere would 
surely bring may have a range of unsuspected practical benefits, particularly to the 
extent that research in cancer and aging is now limited by ideas rather than money. 

The study of the highly condensed matter in neutron stars and the enormous 
energy productions in the centers of galaxies and in quasars has already led to 
suggestions about possible modifications of the laws of physics, laws that have 
been deduced on Earth to explain phenomena observed on Earth. 

The exploration of space will inevitably provide a wealth of practical benefits. 
But the history of science suggests that the most important of these will be 
unexpected - benefits we are today not wise enough to anticipate. 


8. Space Exploration as a Human Enterprise 

II. The Public Interest 

Direct scientific interest in space exploration and the practical consequences that 
can be imagined flowing from them are not the principal or even the most general 
interests that space exploration holds for the layman. There is today - in a time 
when old beliefs are withering - a kind of philosophical hunger, a need to know 
who we are and how we got here. There is an ongoing search, often unconscious, 
for a cosmic perspective for humanity. This can be seen in innumerable ways, but 
most clearly on the college campus. There, an enormous interest is apparent in a 
range of pseudoscientific or borderline-scientific topics - astrology, Scientology, 
the study of unidentified flying objects, investigation of the works of Immanuel 
Velikovsky, and even science-fiction superheroes - all of which represent an 
attempt, overwhelmingly unsuccessful in my view, to provide a cosmic 
perspective for mankind. Professor George Wald, of Harvard, is thinking of this 
longing for a cosmic perspective when he writes: "We have desperately to find our 
way back to human values. I would even say to religion. There is nothing 
supernatural, in my mind. Nature is my religion, and it's enough for me... What I 
mean is: We need some widely shared view of the place of Man in the Universe." 

The most widely sold book in college communities from Cambridge, 
Massachusetts, to Berkeley, California, in recent years was called The Whole Earth 
Catalog, which viewed itself as providing access to tools for the creation of 
cultural alternatives. What was striking was the number of works displayed in the 
Catalog that related to a scientific cosmic perspective. They ranged from the 
Hubble Atlas of Galaxies to flags and posters of Earth photography near full phase. 
The title of The Whole Earth Catalog derives from its founder's urge to see a 
photograph of our planet as a whole. The Fall 1970 issue expanded this 
perspective, showing a photograph of the whole Milky Way Galaxy. 

There is a similar trend apparent in some modern art and in rock 'n' roll music: 
"Cosmo's Factory" by Creedence Clearwater Revival, "Starship" by the Jefferson 
Airplane, "Mr. Spaceman" and "CTA 102" by the Byrds, "Mr. Rocket Man" by 
Elton John, and many others. 

Such interest is not restricted to the young. There is a tradition in the United 
States of public-subscription support of astronomy. Construction of entire 
observatories and salaries for staff have been paid for voluntarily by the local 
communities. Several million people visit planetariums in North America and 
Britain each year. 

The current resurgence of interest in the ecology of the planet Earth is also 
connected with this longing for a cosmic perspective. Many of the leaders of the 
ecological movement in the United States were originally stimulated to action by 
photographs of Earth taken from space, pictures revealing a tiny, delicate, and 


fragile world, exquisitely sensitive to the depredations of man - a meadow in the 
middle of the sky. 

As the results of space exploration and their accompanying new perspectives 
on Earth and its inhabitants permeate our society, they must, I believe, have 
consequences in literature and poetry, in the visual arts and music. The 
distinguished American physicist Richard Feynman writes: "It does no harm to the 
mystery to know a little about it. For far more marvelous is the truth than any 
artists of the past imagined! Why do the poets of the present not speak of it? 
What men are poets who can speak of Jupiter if he were like a man, but if he is an 
immense spinning sphere of methane and ammonia must be silent?" 1 

1 Richard Feynman, Introduction to Physics, Vol. I, Addison Wesley, pp. 3-6. 

But mere general exploration does not yet motivate pervasive public interest in 
space. For many, the rocks returned from the Moon were a great disappointment. 
They were seen as merely rocks. What role they might play in chronicling the days 
of creation of the Earth-Moon system has not yet been explained adequately to 
the public. 

Where public interest in space is most apparent is in cosmology and in the 
search for extraterrestrial life, topics that strike resonant chords in a significant 
fraction of mankind. The fact that much more newspaper space is given to the 
most casual hypothesis on exobiology than to many of the most careful and 
important results in other areas is an accurate reflection of where public interest 
lies. The discovery of interstellar microwave lines of formaldehyde and hydrogen 
cyanide has been widely described in the public press as connected, through a long 
set of linkages, to questions in biology. 

While it is true that the average person thinks in terms of mild variants of 
human beings when he is asked to imagine extraterrestrial life, it is also true that 
interest even in Martian microbes is much larger than in many other areas of space 
exploration. The search for extraterrestrial life could be a keystone of public 
support for space experiments - experiments oriented both within and beyond 
the Solar System. 

There are many possible viewpoints on the present and near-future costs of 
space science and astronomy. Because the annual costs of ground-based astronomy 
are only a few percent of the costs of the scientific space program, I will 
concentrate on the price of the latter. It is customary to compare expenditures on 
space to annual expenditures in the United States for ethyl alcohol or bubble gum 
or cosmetics. I personally find it more useful to compare the costs with those of 
the U. S. Department of Defense. Using a report of the government's General 
Accounting Office (the New York Times, July 19, 1970), we learn that the total 
anticipated cost of the Viking mission to land on Mars in 1976 is about half that of 
the cost overruns in the so-called Safeguard antiballistic missile system for fiscal 
year 1970. The cost of a Grand Tour exploration of all the planets in the outer 
Solar System (canceled for lack of funds) is comparable to the 1970 cost overruns 
on the Minuteman III system; the cost of a very large optical telescope in space, 


capable of definitive studies of the origins of the universe, is comparable to the 
1970 cost overruns on the Minuteman II missile; and a major program of Earth 
resources satellites, involving several years of close inspection of the surface and 
weather of our planet, would cost approximately the fiscal year 1970 cost overruns 
on the P-3C aircraft. A decade-long program of systematic investigation of the 
entire Solar System would cost as much as the accounting mistakes on a single 
"defense" weapons system in a single year. The scientific space program is small 
change compared to the errors in the Department of Defense budget. 

Another viewpoint worth considering is space exploration as entertainment. A 
Viking Mars-lander could be completely funded through the sale, to every 
American, of a single issue of a magazine, containing pictures taken on the surface 
of Mars by V iking. Photographs of the Earth, the Moon, the planets, and spiral and 
irregular galaxies are an appropriate and even characteristic art form of our age. 
Such novel and oddly moving photographs as the Lunar Orbiter image of the 
interior of the crater Copernicus and the Mariner 9 photography of the Martian 
volcanoes, windstreaks, moons, and polar icecaps speak both to a sense of wonder 
and to a sense of art. An unmanned roving vehicle on Mars could probably be 
supported by subscription television. A phonograph record of the output of a 
microphone on Mars, where there seems to be a great deal of acoustic energy, 
might have wide sales. 

I do not wish here to broach the debate on manned vs. unmanned planetary 
exploration, except to stress again that there may be very good nonscientific 
reasons for sending men into space. There exist intermediate cases between 
manned and unmanned exploration, which we may very well see in the 
forthcoming decades. For example, there may be telepuppets, devices landed on 
another planet but fully controlled by an individual human being in orbit, all of 
whose senses are in a feedback loop with the device. It is also possible that planets 
with very hostile environments by terrestrial standards, or planets where there is a 
great danger of contamination by terrestrial micro-organisms, will be explored by 
men inside machines like enormous prosthetic devices, amplifying the sense 
perceptions and muscular abilities of the human operator. 

Even apart from these hypothetical developments, it is already quite clear that 
the development of sophisticated devices for unmanned planetary exploration is 
organizing the same technology required for the production of useful robots on the 
Earth. An unmanned vehicle that lands on Mars by the early 1980s will very likely 
have the ability to sense its environment much more thoroughly than humans are 
able to, to rove over the landscape, to make both preprogrammed decisions and 
decisions based on information newly acquired. First cousins to such a robot, some 
mass-produced, would be extremely useful devices here on Earth. I am thinking in 
part of operations in inaccessible environments such as the abyssal floor of the 
ocean basins, but I am also thinking of industrial robots to free workers from 
repetitive and uninteresting tasks, and domestic robots to liberate the housekeeper 
from a life of drudgery. 


The experience of space exploration gives no unique philosophy; to some 
extent, each group tends to see its own philosophical view reflected, and not 
always by the soundest logic: Nikita Khrushchev stressed that in the space flight of 
Yuri Gagarin no angels or other supernatural beings were detected; and, in almost 
perfect counterpoint, the Apollo 8 astronauts read from lunar orbit the Babylonian 
cosmogony enshrined in Genesis, Chapter 1 , as if to reassure their American 
audience that the exploration of the Moon was not really in contradiction to 
anyone's religious beliefs. But it is striking how space exploration leads directly to 
religious and philosophical questions. 

I believe that military control of manned space flight — in practice in the Soviet 
Union and a subject of current debate in the United States - is a step that 
supporters of peace should back. The military establishments of the United States 
and the Soviet Union are, I am afraid, establishments with vested interests in war. 
They are meticulously trained for war; in time of war, there are rapid promotions, 
increases in pay, and opportunities for valor that are absent in peacetime. Where 
eager readiness for warfare exists, the likelihood of intentional or accidental 
warfare becomes much greater. By virtue of their training and temperament, 
military men are often not interested in other sorts of gainful employment. There 
are few other ways of life with the perquisites of power of the military officer. If 
peace broke out, the officer corps, their services no longer as necessary, would be 
profoundly discomfited. Premier Khrushchev once attempted to cashier a large 
number of senior officers in the Red Army, putting them in charge of 
hydroelectric power stations and the like. This was not to their liking, and in 
something like a year most of them were back in their old jobs. In fact, the 
military establishments in the United States and the Soviet Union owe their jobs 
to each other, and there is a very real sense in which they form a natural alliance 
against the rest of us. 

At the same time, there are enormous labor forces and huge electronics, 
missile, and chemical industries that have an equally strong vested interest in and 
maintain equally strong lobbies for the maintenance of the warfare state. Barring 
some awesomely atypical epidemic of reason, is there not some way that this 
powerful collection of vested interests could be moved toward more peaceful 
activities? Space exploration requires exactly this combination of talents and 
capabilities. It requires a large technical base in such areas as electronics, computer 
technology, precision machinery, and aerospace frames. It requires something very 
close to military organization to keep a large number of geographically dispersed 
enterprises moving in phase toward a common goal. 

The history of the exploration of the Earth's surface has largely been a military 
history, in part because it is an appropriate application of military traditions of 
organization and personal valor. It is the other military traditions that pose a 
danger to us today. Perhaps the exploration of the Solar System is an alternative 
and honorable employment for the military and industrial vested interests. I can 
imagine a transition to an arrangement where a significant fraction of the career 


officer corps of both the United States and the U.S.S.R. is transferred to space 
exploration. At least in part because of their considerable abilities, a fair number 
of military officers are employed by the National Aeronautics and Space 
Administration in activities with little or no military significance. And of course 
the vast majority of astronauts and cosmonauts have been military officers. This is 
surely all to the good: The more of them engaged up there, the less of them 
engaged down here. 

Despite many NASA press releases, much of the space program and almost all 
of its space science and applications program are in the long run not gimmicky or 
parochial in perspective. Indeed, they share a community of philosophical, 
exploratory, and human interest with many segments of American society - even 
segments that are in strong mutual disagreement on many issues. The cost of space 
exploration seems very modest compared with its potential returns. 


Schematic representation of a Type I civilization, perhaps a 
few centuries more advanced than our civilization. By Jon 


9- Space Exploration as a Human Enterprise 

III. The Historical Interest 

In the long view, the greatest significance of space exploration is that it will 
irreversibly alter history. As we mentioned in Chapter 1, the group with which 
Man identifies has gradually broadened during this history of mankind. Today the 
bulk of the world's population has at least a major personal identification with 
national superstates. While progress has not been smooth, and there are occasional 
reversals, the trend is clearly toward a group identification with mankind as a 
whole. Space exploration can hasten this identification. Astronauts and 
cosmonauts have remarked with great feeling about the beauty and serenity of the 
Earth viewed from space. For many of them, a flight into space has been a 
religious experience, transfiguring their lives. National boundaries do not appear in 
photographs of Earth from space. As Arthur C. Clarke somewhere remarked, it is 
difficult to imagine even the most fervent of nationalists not reconsidering his 
views as he sees the Earth fade from a faint crescent to a tiny point of light, lost 
among millions of stars. 

Space exploration provides a calibration of the significance of our tiny planet, 
lost in a vast and unknown universe. The search for life elsewhere will almost 
surely drive home the uniqueness of Man: The winding, unsure, improbable, 
evolutionary pathway that has brought us to where we are; and the improbability 
of finding - even in a universe populated with other intelligences - one with a 
form very much like our own. In this perspective, the similarities among men will 
stand out overwhelmingly against our differences. 

There is a practical geocentrism to our everyday life. We still talk about the 
Sun rising and setting rather than the Earth turning. We still think of the universe 
organized for our benefit and populated only by us. Space exploration will bring 
also a little humility. 

Harold Urey has perceptively referred to the space program as a kind of 
contemporary pyramid-building. Seen in the context of Pharaonic Egypt, the 
analogy seems particularly apt, for the pyramids were an attempt to deal with 
problems of cosmology and immortality. In the long historical perspective, this is 
precisely what the space program is about. The footprints left by astronauts on the 
Moon will survive a million years, and the miscellaneous instruments and packing 
cases left there may last as long as the Sun. 

On the other hand, the pyramids are monumental and, we today believe, futile 
efforts to insure the survival after death of one man, the Pharaoh. Perhaps a better 
analogy is with the ziggurats, the terraced towers of the Sumerians and 
Babylonians - the places where the gods came down to Earth and the population 
as a whole transcended everyday life. There is no doubt a little of the pyramid in 
the great rocket boosters; but I think their ultimate significance is more likely to 
be as contemporary ziggurats. 


A society engaged in a relatively modest, peaceful, and intellectually significant 
exploration of its surroundings garners thereby the possibility of achieving 
greatness. It is difficult to prove such causal chains, and, historically, there are no 
one-to-one correlations. But it is remarkable that the nations and epochs marked 
by the greatest flowering of exploration are also marked by the greatest cultural 
exuberance. In part, this must be because of the contact with new things, new 
ways of life, and new modes of thought unknown to a closed culture, with its vast 
energies turned inward. 

There are examples from the Biblical Near East, from Periclean Athens, and 
from other times, but I am most taken by the example of the age of European 
exploration and discovery. The vernacular languages of France, England, and Iberia 
found a definitive literary expression at the same time that the earliest 
transatlantic voyages of discovery were occurring. Rabelais and Montaigne in 
France; Shakespeare, Milton, and the translators of the King James Bible in 
England; Cervantes and Lope de Vega in Spain; Camoens in Portugal, all date from 
this period. From the writings of Francis Bacon it is clear that exposure to new 
parts of the world had a profound influence on the thinking of the times. This 
period saw the invention of such fundamental instruments as the telescope, the 
microscope, the thermometer, the barometer, and the pendulum clock. 

It was also the epoch of Galileo (1564-1642), who, while not resident in one of 
the new exploratory nations, was closely tied to one of them - Holland, where the 
telescope that he improved upon was first invented. Many of the works of graphic 
art during this period - for example, those of Hieronymus Bosch and El Greco - 
reflect the spirit of change that permeated the times. It was the era of the 
establishment of modern physics by Isaac Newton. Descartes, Hobbes, and 
Spinoza - pivotal individuals in the history of philosophy — flourished. In the 
activities and writings of da Vinci, Gilbert, Galileo, and Bacon, the period also 
corresponds to the origin of the experimental method in science. 

An interesting case history is provided by Holland, a country that has provided 
more than its fair share of men of learning and culture. If there was one moment 
of cultural efflorescence in Holland, it was the period centered around the last half 
of the seventeenth century. Iberian ports were inaccessible to the Dutch Republic 
because of the war between France and Spain. Forced to find its own sources of 
trade, Holland founded the Dutch East and West India Companies. A significant 
fraction of the national resources was put into seafaring; one consequence was that 
Holland became - for the only time in its history - a world power. Because of 
these ventures, Dutch is spoken in Indonesia today, and several individuals of 
Dutch ancestry rose to the Presidency of the United States. Far more important is 
the fact that, during the same period, Vermeer and Rembrandt, Spinoza and van 
Leeuwenhoek flourished in Holland. It was a tightly knit society: Van 
Leeuwenhoek, was, in fact, the executor of Vermeer's estate. Holland was the 
most liberal and least authoritarian nation in Europe during this time. 


In all the history of mankind, there will be only one generation that will be first 
to explore the Solar System, one generation for which, in childhood, the planets 
are distant and indistinct discs moving through the night sky, and for which, in old 
age, the planets are places, diverse new worlds in the course of exploration. 

There will be a time in our future history when the Solar System will be 
explored and inhabited. To them, and to all who come after us, the present 
moment will be a pivotal instant in the history of mankind. There are not many 
generations given an opportunity as historically significant as this one. The 
opportunity is ours, if we but grasp it. To paraphrase K. E. Tsiolkovsky, the 
founder of astronautics: The Earth is the cradle of mankind, but one cannot live in 
the cradle forever. 

A human infant begins to achieve maturity by the experimental discovery that 
he is not the whole of the universe. The same is true of societies engaged in the 
exploration of their surroundings. The perspective carried by space exploration 
may hasten the maturation of mankind — a maturation that cannot come too soon. 


"Les Mystfrcs < 1 « Iufinis" by Grand vi He, 1844. 

Part Two: 


There was a time - and very recently - when the idea of the possibility of 
learning the composition of the celestial bodies was considered senseless even by 
prominent scientists and thinkers. That time has now passed. The idea of the 
possibility of a closer, direct study of the universe will today, I believe, appear still 
wilder. To step out onto the soil of asteroids, to lift with your hand a stone on the 
moon, to set up moving stations in ethereal space, and establish living rings around 
the earth, the moon, the sun, to observe Mars from a distance of several tens of 
versts, to land on its satellites and even on the surface of Mars - what could be 
more extravagant! However, it is only with the advent of reactive vehicles that a 
new and great era in astronomy will begin, the epoch of a careful study of the 
sky. . . The prime motive of my life is to do something useful for people. . . That is 
why I have interested myself in things that did not give me bread or strength. But I 
hope that my studies will, perhaps soon but perhaps in the distant future, yield 
society mountains of grain and limitless power. 


-K. E. Tsiolkovsky, 1912 



io. On Teaching the First Grade 

A friend in the first grade asked me to come to talk to his class, which, he assured 
me, knew nothing about astronomy but was eager to learn. With the approval of 
his teacher, I arrived at his school in Mill V alley, California, armed with twenty or 
thirty color slides of astronomical objects - the Earth from space, the Moon, the 
planets, exploding stars, gaseous nebulae, galaxies, and the like - which I thought 
would amaze and intrigue and, perhaps to a certain extent, even educate. 

But before I began the slide show for these bright-eyed and cherubic little 
faces, I wanted to explain that there is a big difference between stating what 
science has discovered and describing how scientists found it all out. It is pretty 
easy to summarize the conclusions. It is hard to relate all the mistakes, false leads, 
ignored clues, dedication, hard work, and painful abandonment of earlier views 
that go into the initial discovery of something interesting. 

I began by saying, "Now you have all heard that the Earth is round. Everybody 
believes that the Earth is round. But why do we believe the Earth is round? Can 
any of you think of any evidence that the Earth is round?" 

For most of the history of mankind, it was reverently held that the Earth is flat 
- as is entirely obvious to anyone who has stood in a Nebraska cornfield around 
planting time. The concept of a flat Earth is still built into our language in such 
phrases as "the four corners of the Earth." I thought I would stump my little first- 
graders and then explain with what difficulty the sphericity of Earth had come 
into general human consciousness. But I had underestimated the first grade of Mill 
V alley. 

"Well," asked a moppet in the sort of one-piece coverall worn by railroad 
engineers, "what about this business of a ship that's sailing away from you, and the 
last thing you see is the master, or whatever it's called, that holds up the sail? 
Doesn't that mean that the ocean has to be curved?" 

"What about when there's an ellipse of the Moon? That's when the Sun is 
behind us and the shadow of the Earth is on the Moon, right? Well, I saw an 
ellipse. That shadow was round, it wasn't straight. So the Earth has to be round." 

"There's better proof, much better proof," offered another. "What about that 
old guy who sailed around the world - Majello? You can't sail around the world if 
it isn't round, right? And people today sail around the world and fly around the 
world all the time. How can you fly around the world if it isn't round?" 

"Hey, listen, you kids, don't you know there's pictures of the Earth?" added a 
fourth. "Astronauts have been in space, they took pictures of the Earth; you can 
look at the pictures, the pictures are all round. You don't have to use all these 
funny reasons. You can see that the Earth is round." 

And then, as the coup de grace, one pinafored little girl, recently taken on an 
outing to the San Francisco Museum of Science, casually inquired, "What about 
the Foucault pendulum experiment?" 


It was a very sobered lecturer who went on to describe the findings of modern 
astronomy. These children were not the offspring of professional astronomers or 
college teachers or physicians or the like. They were apparently ordinary first- 
grade children. I very much hope — if they can survive twelve to twenty years of 
regimenting "education" - that they will hurry and grow up and start running 

Astronomy is not taught in the public schools, at least in America. With a few 
notable exceptions, a student can pass from first to twelfth grade without ever 
encountering any of the findings or reasoning processes that tell us where we are 
in the universe, how we got here, and where we are likely to be going; without 
any confrontation with the cosmic perspective. 

The ancient Greeks considered astronomy one of the half dozen or so subjects 
required for the education of free men. I find, in discussions with first-graders and 
hippie communards, congressmen and cab drivers, that there is an enormous 
untapped reservoir of interest and excitement in things astronomical. Most 
newspapers in America have a daily syndicated astrology column. How many have 
a daily syndicated astronomy column, or even a science column? 

Astrology pretends to describe an influence that pervades people's lives. But it 
is a sham. Science really influences people's lives, and in only a slightly less direct 
sense. The enormous popularity of science fiction and of such movies as 2001: A 
Space Odyssey is indicative of this unexploited scientific enthusiasm. To a very 
major extent, science and technology govern, mold, and control our lives - for 
good and for ill. We should make a better effort to learn something about them. 


Britannia, the goddess on the obverse face of the old British 


ii. ’’The Ancient and Legendary Gods of Old" 

The sorts of scientific problems that I am involved in — the environments of other 
planets, the origin of life, the possibility of life on other worlds - engage the 
popular interest. This is no accident. I think all human beings are excited about 
these fundamental problems, and I am lucky enough to be alive at a time when it 
is possible to perform scientific investigation of some of these problems. 

One result of popular interest is that I receive a great deal of mail, all kinds of 
mail, some of it very pleasant, such as from the people who wrote poems and 
sonnets about the plaque on Pioneer 10 ; some of it from schoolchildren who wish 
me to write their weekly assignments for them; some from strangers who want to 
borrow money; some from individuals who wish me to check out their detailed 
plans for ray guns, time warps, spaceships, or perpetual motion machines; and 
some from advocates of various arcane disciplines such as astrology, ESP, UFO- 
contact stories, the speculative fiction of von Danniken, witchcraft, palmistry, 
phrenology, tea-leaf reading, Tarot cards, the I-Ching, transcendental meditation, 
and the psychedelic drug experience. Occasionally, also, there are sadder stories, 
such as from a woman who was talked to from her shower head by inhabitants of 
the planet V enus, or from a man who tried to file suit against the Atomic Energy 
Commission for tracking his every movement with "atomic rays." A number of 
people write that they can pick up extraterrestrial intelligent radio signals through 
the fillings in their teeth, or just by concentrating in the right way. 

But over the years there is one letter that stands out in my mind as the most 
poignant and charming of its type. There came in the post an eighty-five-page 
handwritten letter, written in green ballpoint ink, from a gentleman in a mental 
hospital in Ottawa. He had read a report in a local newspaper that I had thought it 
possible that life exists on other planets; he wished to reassure me that I was 
entirely correct in this supposition, as he knew from his own personal knowledge. 

T o assist me in understanding the source of his knowledge, he thought I would 
like to learn a little of his personal history — which explains a good bit of the 
eighty-five pages. As a young man in Ottawa, near the outbreak of World War II, 
my correspondent chanced to come upon a recruiting poster for the American 
armed services, the one showing a goateed old codger pointing his index finger at 
your belly button and saying, "Uncle Sam Wants You." He was so struck by the 
kindly visage of gentle Uncle Sam that he determined to make his acquaintance 
immediately. My informant boarded a bus to California, apparently the most 
plausible habitation for Uncle Sam. Alighting at the depot, he inquired where 
Uncle Sam could be found. After some confusion about surnames, my informant 
was greeted by unpleasant stares. After several days of earnest inquiry, no one in 
California could explain to him the whereabouts of Uncle Sam. 

He returned to Ottawa in a deep depression, having failed in his quest. But 
almost immediately, his life's work came to him in a flash. It was to find "the 
ancient and legendary gods of old," a phrase that reappears many times throughout 


the letter. He had the interesting and perceptive idea that gods survive only so 
long as they have worshipers. What happens then to the gods who are no longer 
believed in, the gods, for example, of ancient Greece and Rome? Well, he 
concluded, they are reduced to the status of ordinary human beings, no longer 
with the perquisites and powers of the godhead. They must now work for a living 
- like everyone else. He perceived that they might be somewhat secretive about 
their diminished circumstances, but would at times complain about having to do 
menial labor when once they supped at Olympus. Such retired deities, he 
reasoned, would be thrown into insane asylums. Therefore, the most reasonable 
method of locating these defrocked gods was to incarcerate himself in the local 
mental institution - which he promptly did. 

While we may disagree with some of the steps in his reasoning, we probably all 
agree that the gentleman did the right thing. 

My informant decided that to search for all the ancient and legendary gods of 
old would be too tiring a task. Instead, he set his sights on only a few: Jupiter, 
Mercury, and the goddess on the obverse face of the old British penny - not 
everyone's first choice of the most interesting gods, but surely a representative trio. 
To his (and my) astonishment, he found - incarcerated in the very asylum in 
which he had committed himself - Jupiter, Mercury, and the goddess on the 
obverse face of the old English penny. These gods readily admitted their identities 
and regaled him with stories of the days of yore when nectar and ambrosia flowed 

And then my correspondent succeeded beyond his hopes. One day, over a 
bowl of Bing cherries, he encountered "God Almighty," or at least a facsimile 
thereof. At least the Personage who offered him the Bing cherries modestly 
acknowledged being God Almighty. God Almighty luckily had a small spaceship 
on the grounds of the asylum and offered to take my informant on a short tool 
around the Solar System - which was no sooner said than done. 

"And this, Dr. Sagan, is how I can assure you that the planets are inhabited." 

The letter then concluded something as follows: "But all this business about life 
elsewhere is so much speculation and not worth the really serious interest of a 
scientist such as yourself. Why don't you address yourself to a really important 
problem, such as the construction of a trans-Canadian railroad at high northern 
latitudes?" There followed a detailed sketch of the proposed railway route and a 
standard expression of the sincerity of his good wishes. 

Other than stating my serious intent to work on a trans-Canadian railroad at 
high northern latitudes, I have never been able to think of an appropriate response 
to this letter. 


Radar map of the surface of Venus, unseen by the human 
eye because of the dense atmosphere and cloud cover of the 
planet. Courtesy. Arecibo Observatory, Cornell University. 


12. The Venus Detective Story 

One of the reasons that planetary astronomy is such a delight these days is that it 
is possible to find out what's really right. In the old days, you could make any 
guess you liked, however improbable, about a planetary environment, and there 
was little chance that anyone could ever prove you wrong. Today, spacecraft hang 
like swords of Damocles over each hypothesis spun by planetary theoreticians, and 
the theoreticians can be observed in a curious amalgam of hope and fear as each 
new burst of spacecraft planetary information comes winging in. 

Back when astronomers had telescopes, eyeballs, and very little else to assist 
their observations, Venus beckoned as a sister world. By the late nineteenth 
century, it was known that Venus had about the same mass and radius as Earth. 
Venus is the closest planet to Earth, and it was natural to assume that it was, in 
other respects, Earth-like. 

Immanuel Kant imagined a race of amorous quasi-humans on Venus. Emanuel 
Swedenborg and Annie Besant, a founder of theosophy, found - by methods 
described as spirit travel and astral projection - creatures very like humans on 
Venus. In more recent years, some of the more spectacularly audacious flying- 
saucer accounts - for example, those of George Adamski - populated Venus with 
a race of benign and powerful beings, many of whom seem to have been garbed in 
long hair and long white robes - clear symbolism, in pre-1963 America, of deep 
spiritual intent. There is a long history of wishful thinking, bemused speculation, 
and conscious and unconscious fraud, which produced a popular expectation that 
our nearest planetary neighbor is habitable by humans, and is possibly even already 
inhabited by creatures rather like us. 

It was, therefore, with a sense of considerable surprise, and even annoyance, 
that the results of the first radio observations of Venus were greeted. These 
measurements, performed in 1956 by C. H. Mayer and colleagues at the U. S. 
Naval Research Laboratory, found Venus to be a much more intense source of 
radio emission than had been expected. From Venus' distance to the Sun and the 
amount of sunlight it reflects back to space, the planet should be cool. Because 
Venus reflects so much sunlight back to space, its temperature ought to be even 
less than the Earth's, despite its closeness to the Sun. Mayer's group found that 
V enus, at a radio wavelength of 3 centimeters, was giving off as much radiation as 
it would if it were a hot body at a temperature of about 600 degrees Fahrenheit. 
Later observations with many different radio telescopes at many different radio 
frequencies confirmed the general conclusion that Venus had a "brightness 
temperature" of about 600 degrees to 800 degrees. 

Nevertheless, there was great reluctance in the scientific community to believe 
that the radio emission came from the Venus surface. A hot object emits radiation 
at many wavelengths. Why did Venus seem hot only at radio wavelengths? How 
could the surface of Venus be kept so hot? And finally - since psychological 
factors may be unconsciously compelling, even in science - a Venus hotter than 


the hottest household oven is simply less pleasant a prospect than the Venus 
populated, in the long tradition from Kant to Adamski, by gracious humans of 
amorous or spiritual inclinations. 

This problem of the origin of the Venus radio emission was a major part of my 
doctoral dissertation. I wrote some twenty scientific papers concerning it between 
1961 and 1968, when the problem was finally considered settled. I look back on 
this period with pleasure. The Venus radio story is very much like a detective 
story where there are clues littering the pages. Some are vital to the solution; 
others are false clues, leading in the wrong direction. Sometimes the right answer 
can be deduced by bearing in mind all the relevant facts and requiring reasonable 
logical consistency and plausibility. 

There were several things we knew about Venus. We knew how the 
brightness temperature varied with radio frequency. We knew how Venus 
reflected back to Earth radio waves sent out by large radar telescopes. Man's first 
successful planetary probe — the United States' Mariner 2 — found in 1962 that 
Venus was brighter at radio wavelengths at its center than at its edge. 

To be matched against such observations were a variety of theories. They fell 
into two general categories: The hot-surface model, in which the radio emission 
came from the solid surface of the planet; and the cold-surface model, in which 
the radio emission came from somewhere else - from an ionized layer in the 
atmosphere of V enus, or from electrical discharges between droplets in the clouds 
of V enus, or from a hypothesized great belt of rapidly moving electrically charged 
particles surrounding Venus (like those that, in fact, surround the Earth and 
Jupiter). These latter models permitted the surface to be cold by placing the 
intense radio emission above the surface. If you wanted sailing ships on Venus, 
you were a cold-surface model advocate. 

We systematically compared the cold-surface models with the observations 
and found that they all ran into serious troubles. The model in which the radio 
emission came from the ionosphere, for example, predicted that Venus should not 
reflect radio waves at all. But radar telescopes had found radio waves reflected 
from Venus with an efficiency of 10 or 20 percent. To circumvent such 
difficulties, advocates of the ionospheric model constructed very elaborate 
hypotheses in which there were many ionized layers with especially constructed 
holes in them to let radar through the ionosphere, hit the surface of Venus, and 
return to Earth. At the same time there could not be too many holes; otherwise, 
the radio emission would not be as intense as observed. These models seemed to 
me to be far too detailed and arbitrary in their requirements. 

Just before the remarkable spacecraft observations of Venus of 1968, I 
submitted a paper to Nature, the British scientific journal, in which I summarized 
these conclusions and deduced that only the hot-surface model was consistent 
with all the evidence. I had earlier proposed a specific theory, in terms of the 
greenhouse effect, to explain how the surface of Venus could be at such high 
temperatures. But my conclusions against cold-surface models in 1968 did not 


depend upon the validity of the greenhouse explanation: It was just that a hot 
surface explained the data and a cold surface did not. Because of my interest in 
exobiology, I would have preferred a habitable Venus, but the facts led elsewhere. 
In a paper published in 1962, I had concluded from indirect evidence that the 
average surface temperature on Venus was about 800 degrees F and the average 
surface atmospheric pressure about fifty times larger than at the surface of Earth. 

In 1968, an American spacecraft, Mariner 5, flew by Venus, and a Soviet 
spacecraft, Venera 4, entered its atmosphere. By the year 1974 there had been five 
Soviet instrumented capsules that entered the Venus atmosphere. The last three 
touched down and returned data from the planetary surface. They were the first 
craft of mankind to land on the surface of another planet. The average 
temperature on Venus turns out to be about 900 degrees F; the average pressure 
at the surface appears to be about ninety atmospheres. My early conclusions were 
approximately correct, just slightly too conservative. 

It is interesting, now that we know by direct measurements the actual 
conditions on Venus, to read some of the criticism of the hot-surface model 
published in the 1960s. The year after receiving my Ph.D., I was offered, by a well- 
known planetary astronomer, ten-to-one odds that the surface pressure on Venus 
was no more than ten times that on Earth. I gladly offered my ten dollars against 
his hundred; to his credit, he paid off - after the Soviet landing observations were 
in hand. 

Theory and spacecraft interact in other ways. For example, Venera 4 radioed its 
last temperature/ pressure point at 450 degrees F and twenty atmospheres. The 
Soviet scientists concluded that these were the surface conditions on Venus. But 
ground-based radio data had already shown that the surface temperature must be 
much higher. Combining radar with Mariner 5 data, we knew that the surface of 
Venus was far below where the Soviet scientists concluded Venera 4 had landed. 
It now appears that the designers of the first Venera spacecraft, believing the 
models of cold-surface theoreticians, built a relatively fragile spacecraft, which was 
crushed by the weight of the Venus atmosphere far above the surface - much as a 
submarine, not designed for great depths, will be crushed at the ocean bottoms. 

At the 1968 Tokyo meeting of COSPAR, the Committee on Space Research of 
the International Council of Scientific Unions, I proposed that the Venera 4 
spacecraft had ceased operating some fifteen miles above the surface. My 
colleague, Professor A. D. Kuzmin, of the Febedev Physical Institute, in Moscow, 
argued that it had landed on the surface. When I noted that the radio and radar 
data did not put the surface at the altitude deduced for the Venera 4 touchdown, 
Dr. Kuzmin proposed that Venera 4 had landed atop a high mountain. I argued 
that ground-based radar studies of Venus had shown mountains a mile high, at 
most, and that it was exceptionally unlikely Venera 4 would land on the only 
fifteen-mile-high mountain on Venus, even if such a mountain were possible. 
Professor Kuzmin replied by asking me what I thought was the probability that 
the first German bomb to fall on Feningrad in World War II would kill the only 

7 2 

elephant in the Leningrad zoo. I admitted that the chance was very small, indeed. 
He responded, triumphantly, with the information that such was indeed the fate 
of the Leningrad elephant. 

The designers of subsequent Soviet entry probes were, despite the Leningrad 
zoo, cautious enough to increase the structural strength of the spacecraft in each 
successive mission. Venera 7 was able to withstand pressures of 180 times that at 
the surface of the Earth, a quite adequate margin for the actual Venus surface 
conditions. It transmitted twenty minutes' worth of data from the Venus surface 
before being fried. Venera 8, in 1972, transmitted more than twice as long. The 
surface pressure is not at twenty atmospheres, and the spectacular Mount Kuzmin 
does not exist. 

The principal conclusion about the scientific method that I draw from this 
history is this: While theory is useful in the design of experiments, only direct 
experiments will convince everyone. Based only on my indirect conclusions, there 
would today still be many people who did not believe in a hot Venus. As a result 
of the Venera observations, everyone acknowledges a V enus of crushing pressures, 
stifling heat, dim illumination, and strange optical effects. 

That our sister planet should be so different from Earth is a major scientific 
problem, and studies of Venus are of the greatest interest in understanding the 
earliest history of Earth. In addition, it helps to calibrate the reliability of astral 
projection and spirit travel of the sorts popularized by Emanuel Swedenborg, 
Annie Besant, and innumerable present-day imitators, none of whom caught a 
glimmering of the true nature of V enus. 


13. Venus Is Hell 

The planet Venus floats, serene and lovely, in the sky of Earth, a bright pinpoint 
of yellowish-white light. Seen or photographed through a telescope, a featureless 
disc is discerned; a vast unbroken and enigmatic cloud layer shields the surface 
from our view. No human eye has seen the ground of our nearest planetary 

But we now know a great deal about Venus. From radio telescope and space- 
vehicle observations, we know that the surface temperature is about 900 degrees 
Fahrenheit. The atmospheric pressure at the surface of Venus is about ninety 
times that which we experience at the surface of the Earth. Since the planet's 
gravity is about as strong as the Earth's, there are about ninety times more 
molecules in the atmosphere of V enus as in the atmosphere of Earth. This dense 
atmosphere acts as a kind of insulating blanket, keeping the surface hot through 
the greenhouse effect and smoothing out temperature differences from place to 
place. The pole of V enus is probably not significantly colder than its equator, and 
on V enus it is as hot at midnight as at noon. 

Forty miles above the surface is the thick cloud layer that we see from Earth. 
At least until recently, no one knew the composition of these clouds. I had 
proposed that they were constituted in part of water, a cosmically very abundant 
material, which could account for many but by no means all of the observed 
properties of the Venus clouds. But there were many other candidate materials 
proposed, among them, ammonium chloride, carbon suboxide, various silicates 
and oxides, solutions of hydrochloric acid, a hydrated ferric chloride, 
carbohydrates, and hydrocarbons. These last two materials were proposed by 
Immanuel Velikovsky in his speculative romance Worlds in Collision to provide 
manna for the Israelites during their forty years of wandering in the desert. The 
other candidate materials were proposed on somewhat firmer grounds. Y et each of 
them ran afoul of one or more of the observations. 

But recently a material has been proposed that is in excellent quantitative 
agreement with all of the measurements. The American astronomer Andrew T. 
Y oung has shown that the clouds of V enus are very likely a concentrated solution 
of sulfuric acid. A 75 percent solution of H 2 S 0 4 precisely matches the index of 
refraction of the Venus clouds determined by polarimetric observations from the 
Earth. None of the other materials comes close. Such a solution is liquid at the 
temperatures and pressures at which the Venus clouds reside. Sulfuric acid has an 
absorption feature, determined by infrared spectroscopy, at a wavelength of 11.2 
microns. Of all the materials proposed, only H 2 S 0 4 has such an absorption feature. 
The Soviet entry spacecraft of the Venera series have found large quantities of 
water vapor below the visible clouds of Venus. Ground-based observers looking 
for water vapor spectroscopically have found only a tiny amount of water vapor 
above the clouds of Venus. The two observations are in accord only if a very 


effective drying agent is present between these two regions. Sulfuric acid is such 
an agent. 

In the Earth's atmosphere there are water droplets at altitude, and water vapor 
in the atmosphere below. Likewise on Venus: If there are sulfuric acid droplets in 
the high clouds, there must be gaseous sulfuric acid below, with a relatively high 
concentration near the surface. Astronomers in Earth-bound observatories have 
also found unmistakable evidence of hydrochloric acid and hydrofluoric acid as 
gases in the upper atmosphere of Venus. They also must exist in a fair 
concentration — for example, the relative proportions of Los Angeles smog in Los 
Angeles air - in the lower atmosphere of Venus. These three acids are an 
extremely corrosive mixture. Any spacecraft that is to survive on the Venus 
surface must not only be bulwarked against the high pressures but protected 
against the corrosive atmosphere. 

The Soviet Union is engaged in a very active program of unmanned exploration 
of V enus. W e now know there is enough light for photography at midday on the 
V enus surface. The time will come, in not too many years, I think, when we will 
have our first photographs of the surface of Venus. What does the surface of 
Venus look like? To some extent we can already make predictions. 

Because of the very dense atmosphere of Venus, there are some interesting 
optical effects. The most important such effect is due to Rayleigh scattering, 
named after the British Lord Rayleigh. When sunlight strikes the clear, dust-free 
atmosphere of the Earth, it is scattered. Photons strike the molecules of the Earth's 
atmosphere and are bounced off. Many such bounces may occur. But because the 
molecules of air are very much smaller than the wavelength of light, it turns out 
that short wavelengths are scattered or bounced away by the air molecules more 
efficiently than long wavelengths. Blue light is scattered much better than red 
light. This was a fact known to Leonardo da V inci, who painted distant landscapes 
in an exquisite cerulean blue. It is why we talk of purple mountains; it is why the 
sky is blue. The light from the sun is scattered about in our atmosphere - some of 
it being scattered up and out again, but other fractions of sunlight being scattered 
about by the molecules of our atmosphere and then, from quite a different 
direction than that of the Sun, scattered back down to our eyeballs. In the absence 
of an atmosphere, as on the Moon, the sky is black. When we look at a sunset we 
are seeing the Sun through a longer path in the Earth's atmosphere than when we 
view it at noon. Blue light has been preferentially scattered out of this path, 
leaving only the red light to strike our eyes. The beauty of the sunset, the sky, and 
distant landscapes are all due to Rayleigh scattering. 

What about Rayleigh scattering on Venus? Because the atmosphere is so much 
denser, Rayleigh scattering there is much more important. Were we to strip the 
clouds off Venus, we would still be unable to see its surface from above. Visible 
light of all colors would be scattered so many times in the Venus atmosphere that 
no image of any surface details would be discerned. In the near infrared, at 
wavelengths longer than the human eye is sensitive to, the surface could, however, 


be seen from above. But there are clouds. Radio waves penetrate the clouds and 
the atmosphere of Venus and the first radar maps of Venus are being developed 
(see page 80). In a few years, Cornell University's great Arecibo telescope in 
Puerto Rico will begin mapping the surface of Venus by radar with higher 
precision than the best ground-based optical maps of the Moon. Already, there are 
hints of mountain ranges and great impact basins on the surface of this enigmatic 

At the surface of Venus, Rayleigh scattering is also an extremely important 
effect. Just as we cannot see the surface in visible light from above Venus, we 
cannot see the sun in visible light from the surface of V enus - even if there were a 
break in the clouds. If there were intelligent life on Venus, astronomy would be 
very slow to develop; and radio astronomy would emerge first. The Venera 8 
spacecraft found that sunlight does reach the surface of V enus during the day, but 
it is so attenuated by passage through the clouds and atmosphere that, even at 
midday, it is no brighter on Venus than at twilight on the Earth. The sunlight 
would be a hazy and diffuse patch of deep ruby-red light, whose rising and setting 
could only indistinctly be determined. 

If you were standing in some protective suit on the surface of Venus and put 
on violet sunglasses, you would see no farther than a few dozen feet. The Rayleigh 
scattering in blue light is so strong on Venus that the visibility in the violet is 
small. But because long wavelength light is scattered less than blue, at the extreme 
red end of the visible spectrum - with red sunglasses on — you could see perhaps a 
thousand feet. At the surface of V enus everything would be suffused in a deep red 
gloom. We would have a perception of color, but only for objects very close to us. 
Our surroundings would be an indistinct roseate blur. 

Venus thus seems to be a place quite different from the Earth, and alarmingly 
unappealing: Broiling temperatures, crushing pressures, noxious and corrosive 
gases, sulfurous smells, and a landscape immersed in a ruddy gloom. 

Curiously enough, there is a place astonishingly like this in the superstition, 
folklore and legends of men. We call it Hell. In the older belief - that of the 
Greeks, for example - it was the place where all human souls journeyed after 
death. In Christian times it has been thought of as the post-mortem destination 
only of one of two categories of moral persuasion. But there is little doubt that the 
average person's view of Hell — sizzling, choking, sulfurous, and red — is a dead 
ringer for the surface of V enus. 

Although terrestrial biological molecules would fall to pieces rapidly on Venus, 
there are organic molecules - for example, some with a complex ring structure - 
that would be quite stable under the conditions of V enus. It is difficult to exclude 
life there, but we can certainly say it would be quite different from what we are 
familiar with. Any organism that lives there would be wise to have leathery skin. 
Because of the high atmospheric pressures, it would even make sense to have little 
stubby wings, which could carry their possessors about without exceptionally 
strenuous flapping. A devil is a very good model - except for his mannish and 


goaty aspects - for an inhabitant of Venus. Milton and Isaiah called Lucifer "Son of 
the Morning," the morning star. For thousands of years Venus and Hell have been 

This is all a very curious coincidence, but I cannot bring myself to think that it 
is anything more than that. The chief point is that in all the legends one gets to 
Hell by going down, not up. The classical world of Greece and Rome and the 
ancient Near East were peppered with active volcanoes. Such volcanic terrains, 
like in contemporary Iceland and Hawaii, are bleak, desolate, and eerily beautiful 
landscapes. Sulfurous gases emanate from volcanic vents; lava fountains and flows 
suffuse the surroundings in red. It is very hot: You singe your eyebrows if you get 
too close to the lava in a collapsed lava tube. And all this heat, redness, and smell 
come from down below. It was not very difficult for our ancestors to imagine that 
volcanic terrains were apertures to a quite different igneous world called Hell. 

The inside of the Earth and the outside of Venus are alike but not identical. 
They are both unpleasant for humans. But they are both of extreme scientific 
interest - worth at least an extended visitation, if not a homesteading. Dante knew 
about that. 


Assorted foreign military attaches assembled to view the 
Aftollo IS launch. Photograph by the author. 


14. Science and "Intelligence" 

I spent my first two postdoctoral years at the University of California, Berkeley, 
where, among other things, I was concerned with searching for life elsewhere and 
with the sterilization of space vehicles intended for places like Mars — we wished 
not to contaminate the Martian environment with microbes from Earth. 

One bright spring day I received a phone call from an Air Force general whom 
I had met at several scientific meetings. He had been working chiefly on aviation 
medicine; I will call him here Bart Doppelganger. General Doppelganger informed 
me that he was in Los Angeles with three Soviet scientists, one of whom was in 
charge of the Soviet effort for constructing instruments to search for 
extraterrestrial life. His name was Alexander Alexandrovitch Imshenetsky (there 
is no reason to change his name; unlike some others in this narrative he has 
nothing to be ashamed of). It was Imshenetsky's first visit to the United States. 
Yes, I would certainly be interested in meeting him. When? The answer was 
"immediately." So I drove to San Francisco airport, flew to Los Angeles, and took a 
taxi to an address given to me by our General Doppelganger. 

It was the home of a professionally well-known UCLA brain physiologist. In 
the living room, upon my arrival, were the physiologist, other aviation medicine 
experts from UCLA, General Doppelganger, three Soviet scientists (two in 
aviation medicine and Academician Imshenetsky), and a translator. I will call the 
translator Igor Rogovin; he was an American employee of the Library of Congress 
assigned to do translation for the three Russians on their visit to the United States. 
The only thing that struck me as somewhat peculiar was that the English of all 
three Russians was quite good. So why a translator? 

Everyone was jolly, pleasantries were exchanged, drinks made the rounds - and 
Igor Rogovin also made the rounds. There was no conversation from which he was 
absent for more than a few minutes. He was very busy, like a manic bee 
obsessively flitting from flower to flower. 

After a while, the plan was for all of us to drive to Los Angeles International 
Airport, where the Russians were later to catch a plane. Before their flight, we 
were all to have dinner. There were more of us than could fit into one car, and 
Rogovin could not easily ride in both cars at once. Imshenetsky, some others, and I 
rode in one car, and Rogovin and the others in a second. During the twenty- or 
thirty-minute drive, Imshenetsky and I had a fruitful exchange of views on 
methods of life detection and space- vehicle sterilization technology. It was the first 
such contact I had had with a Soviet scientist. 

We arrived at the airport, bags were checked, and the Soviets excused 
themselves to go to the men's room. Waiting outside, I found myself alone with 
Igor Rogovin - who immediately said to me out of the corner of his mouth, and in 
a style of vocalization that went out with James Cagney and Humphrey Bogart, 
"Hey, kid, what'd ya find out?" 


Being unwise in the ways of the world, and pleased with the information 
Imshenetsky and I had exchanged, I rapidly summarized what I had learned. 

"Pretty good, kid. Who do you work for?" 

"The University of California at Berkeley," I replied brightly. 

"No, no, kid, not the cover." 

Igor Rogovin's occupation, if not his identity, gradually dawned on me. With a 
rising fury I explained to him that it was possible to have a conversation with a 
Soviet scientist that was intended for the benefit of science rather than for the 
benefit of American military intelligence services. Before Rogovin could reply, our 
friendly Soviet guests re-emerged, and we all went off to dinner. 

Although seated again next to Imshenetsky, I found myself unable to talk to 
him on any subject remotely approaching science. As I recall, our primary topics 
of conversation were American films and Soviet poets. After a number of drinks, 
Alexander Alexandrovitch Imshenetsky offered the opinions that William 
Shakespeare was the leading Russian poet and American cowboy films were 
excessively violent. Several hours easily could be spent discussing these two 
propositions. As the Russians left to fly home, I returned to Berkeley. 

The next morning, I turned to the white pages of the San Francisco telephone 
directory and, under "United States Government," found a section marked 
"Central Intelligence Agency." On dialing the number indicated I encountered a 
cheerful voice that said something like "Yukon 4-2143." 

"Hello, Central Intelligence Agency?" I said. 

"What can we do for you, sir?" 

"I have a complaint to file." 

"One moment, sir, I will give you our Complaint Department." This was 
shortly after the Bay of Pigs, and I guess they had been getting a lot of complaints. 

Upon reaching - yes - the Complaint Department, I rapidly launched into a 
synopsis of my encounter with Mr. Rogovin, but was quickly silenced with an 
injunction that this was not the sort of thing one talked about over the telephone. 
I suppose his phone was tapped. We made an appointment for later that afternoon 
in my office. 

Sure enough, at the prescribed time, two neatly dressed business-suited young 
men arrived, bearing plastic identification cards with the signature of John 
McCone, who had recently been appointed Director of the Central Intelligence 
Agency. After expressing my general annoyance by an exceptionally long scrutiny 
of their IDs, I launched into my story. In their faces was mounting concern. At the 
conclusion of my narrative, they explained to me that Rogovin's behavior was very 
unlikely to be the behavior of any employee of "the agency." They were very 
concerned about such a story, particularly after the "bad press" they had been 
getting about the Bay of Pigs. They would do everything to track the story down if 
I would not embarrass the agency by further disseminating the story. I agreed to 
keep quiet, for a while, and they departed. 


About a week later I received a phone call: "Dr. Sagan, this is Mr. Smith, who 
was in your office last week. You recall the matter about which we talked?" I 
gathered that his phone was still tapped. 

"We have been able to establish that the party in question - you know who I 
mean? — does not work for our organization under that name. We are, of course, 
pursuing other names and will get back to you as soon as we can." 

It had taken them a week to scrutinize the personnel roster of the Central 
Intelligence Agency. The roster must either be very long or very secret. 

Several days later, in similarly veiled language, I was called and told - in a voice 
that seemed to express considerable concern - that Igor Rogovin did not work for 
the CIA under any name whatever, and that they were, under the circumstances, 
naturally curious to know for whom he did work. 

After another week had passed, the CIA made an appointment to speak with 
me once again in my office. The same two gentlemen arrived, again bearing the 
same two plastic cards signed by John McCone. They informed me that, after 
exhaustive investigations, they had discovered that Igor Rogovin, while nominally 
working for the Library of Congress, was, in fact, an employee of Air Force 
Intelligence. They again assured me that no representative of their agency would 
ever behave in so uncouth a manner, and departed. What stood out most clearly 
was that it had taken about two weeks for the Central Intelligence Agency to 
determine the employment of a member of a fellow U.S. intelligence organization. 

This story has a coda. A year or two later the international space organization, 
COSPAR, was meeting in Florence, Italy. In one of the splendid side benefits of 
such meetings, the Uffizi Gallery was opened one evening especially for the 
members of the COSPAR delegations from various nations. As chance would have 
it, I was with Alexander Alexandrovitch Imshenetsky as we entered an enormous 
and apparently empty Botticelli-inundated gallery. And there, at the other end of 
the gallery, a human figure could dimly be perceived. I felt Imshenetsky stiffen. 
Peering intently, I could now make out the visage of Igor Rogovin, his face 
disguised by a beard. He was, no doubt, traveling incognito. Imshenetsky leaned 
over to me and whispered, "Isn't that the fellow who was with us in Los Angeles?" 
When I nodded assent, Imshenetsky murmured, "Very stupid fellow." 

That Rogovin was working for Air Force Intelligence is, in retrospect, not so 
surprising, since I had been invited to Los Angeles by General Doppelganger. That 
Soviet plans for the search for life elsewhere or for the sterilization of spacecraft 
could be considered of interest to Air Force Intelligence is perhaps more 
surprising. That American intelligence agencies would attempt to use 
comparatively innocent young scientists (I was twenty-seven and politically 
unsophisticated) to carry out such a purpose is appalling. At least it appalls me. 

There are many other such stories involving both American and Soviet 
intelligence organizations. The general effect of such incidents is to detract from 
the credibility of legitimate scientific exchanges among scientists of different 
countries. Such exchanges are particularly necessary in an age that hangs a thread 


away from nuclear destruction, and in which scientists have access to at least half 
an ear of the politicians in power. The fact that such intelligence activities are 
practiced in an entirely regular and invariable manner on the Soviet side does not, 
in my view, weaken this argument. The intrusion of "intelligence" into 
international scientific exchanges of this sort is, whatever else it is, just not 


15. The Moons of Barsoom 

In my boyhood I was lucky enough to come upon a set of turgidly written novels 
with names like Thuvia, Maid of Mars, The Chessman of Mars, The Princess of 
Mars, The Warlords of Mars, and so on. They were, needless to say, about Mars. 
But they were not about our Mars - the Mars revealed by Mariner 9. 

At least I don't think our Mars is like the Mars of these novels by Edgar Rice 
Burroughs, the inventor of Tarzan. His Mars was Percival Lowell's Mars - a planet 
of ancient sea bottoms, working canals and pumping stations, six-legged beasts of 
burden, and men (some headless) of all colors, including green. They had names 
like T ars T arkas. Possibly the most remarkable hypothesis proposed by Burroughs 
in these novels was that human beings and inhabitants of Mars could produce live 
offspring - a biologically impossible proposition if the Martians and we are 
imagined as having separate biological origins. Burroughs wrote decorously of the 
interfertility of a Virginian miraculously transported to Mars and Dejah Thoris, the 
princess of a kingdom with the improbable name of Helium. I have little doubt 
that the precedent of a kingdom called Helium led directly to the planet called 
Krypton, home of the comic-book hero Superman. There is here a rich vein of 
untapped literary ore. The future may hold planets, stars, or even entire galaxies 
named Neon, Argon, Xenon, and Radon - the remaining noble gases. 

But the name invented by Burroughs that has haunted me across the years is 
the name he imagined the Martians gave to Mars: Barsoom. And it was one phrase 
of his more than any other that captured my imagination: "The hurtling moons of 

For Mars is indeed a world with two moons - a situation that would appear to 
the inhabitants of Mars as entirely natural as our one Moon does to us. We know 
how our solitary satellite looks to the naked eye from the surface of Earth. But 
what do the moons of Barsoom look like from the surface of Mars? This question, 
which intermittently plagued my boyhood, was not to be answered until 1971 and 
Mariner 9. 

The moons of Mars were invented by Johannes Kepler, the discoverer of the 
laws of planetary motion and no intellectual lightweight. But he lived in the 
sixteenth century, in a different intellectual climate from the present. He cast 
horoscopes for a living; astronomy was his passion more than his occupation. His 
mother was tried as a witch. When Kepler learned of Galileo's discovery, with one 
of the first astronomical telescopes, of the four large moons of Jupiter, he 
immediately concluded that Mars had two moons. Why? Because Mars was at an 
intermediate distance from the Sun, between Earth and Jupiter. It must obviously 
have an intermediate number of moons. The observations seemed to show Venus 
with no moons, Earth with one, and Jupiter with four (the actual number, we 
now know, is twelve). Kepler could have deduced either two or three moons for 
Mars. But bearing a lifelong passion for geometrical progressions, he chose two. 


The argument is, of course, fallacious. Saturn's ten moons, Uranus' five, and 
Neptune's two in no way fit his scheme, which is not scientific but aesthetic. 

But Kepler's prestige was immense, particularly after Kepler's laws of planetary 
motion were derived from gravitational theory by Isaac Newton; and so, literary 
allusions to the two moons of Mars fluttered down the centuries. In Voltaire's 
longish short story "Micromegas" a denizen of the star Sirius notes casually, while 
touring our Solar System, that Mars had two moons. There is a more famous 
reference to two Martian moons in Jonathan Swift's satire of 1726, Gulliver's 
Travels — not the part about the very small people, or the part about the very large 
people, or the part about the intelligent horses, but a less widely read part — the 
part about the floating aerial island of Laputa. The episode is undoubtedly a tightly 
reasoned critique of English-Spanish relations in Swift's time, because la puta is 
Spanish for prostitute. The political metaphors are obscure, at least to me. At any 
rate, Swift announces casually that astronomers on Laputa have discovered two 
swiftly moving moons of Mars, and have provided information on their distances 
from Mars and their periods of revolution about Mars — information that is 
incorrect, but that is not a bad guess. There is an entire genre of writing on how it 
was that Swift knew about the moons of Mars, including the suggestion that he 
was a Martian. Internal evidence suggests that Swift was no Martian, and the two 
moons can almost certainly be traced directly back to Kepler's speculations. 

The actual discovery of the moons of Mars was made from outside 
Washington, D.C., in 1877. The U. S. Naval Observatory had just completed a 
large refracting telescope. The observatory's astronomer, Asaph Hall, sought to 
learn whether the moons of Mars, fabled in song and story, actually existed. His 
first few nights were unsuccessful, and, in a despondent mood, he announced to 
his wife his intention of quitting the search. Mrs. Hall would have none of this, 
and urged her reluctant husband back to a few more nights at the telescope — 
whence he emerged with two Martian satellites in hand. For a brief period he 
thought he had found three satellites, because the inner one moved so rapidly that 
on one night he saw it on one side of Mars and on the next night on the other. 
Hall named the moons Phobos and Deimos, after the horses that pulled the 
chariot of the god of war in Greek mythology; they have the cheerful denotations 
of fear and terror, respectively. (The appropriate adjectives pose some problems: 
Do we talk of Phobic orbits and Deimonic nights?) If another moon of Mars is 
someday found, I hope we will give it a less ferocious and more optimistic name - 
like "Pax." 

I also hope that when the features on Phobos and Deimos are eventually 
named by the International Astronomical Union, one will be named after Mrs. 
Hall. But since another feature will surely be named after Asaph Hall, we have a 
problem - two craters named Hall would be confusing. In an astronomy talk I 
gave at Harvard University, I commented wistfully that the problem would be 
solved if only we knew Mrs. Hall's maiden name. My friend Owen Gingerich, 
Professor of the History of Science at Harvard, instantly leaped to his feet with the 


words "Angelina Stickney" tripping off his lips. So when the time comes, I hope 
there will be a "Stickney" on one of the moons of Barsoom. 

The subsequent study of Phobos and Deimos between 1877 and 1971 has a 
curious history. The moons of Mars are so tiny that they appear, even to the 
largest Earthbound telescopes, as dim points of light. They are too faint for the 
pre-1877 telescopes to have seen them at all. Their orbits can be calculated by 
noting their positions at various times. In 1944 at the U. S. Naval Observatory 
(where an understandably proprietary interest in Phobos and Deimos must have 
developed), B. P. Sharp less collected all the observations available in his day to 
determine the orbits to the best possible precision. He found - no doubt to his 
surprise — that the orbit of Phobos appeared to be decaying, what astronomers call 
a secular acceleration. Over longish periods of time the satellite seemed to be 
approaching more and more closely to Mars and moving more and more rapidly. 
This phenomenon is quite familiar to us today. The orbits of artificial satellites are 
decaying all the time in the Earth's atmosphere. They are initially slowed by 
collisions with the diffuse upper atmosphere of the Earth, but by Kepler's laws the 
net result is a more rapid motion. 

Sharpless' conclusion of a secular acceleration for Phobos remained an 
unexplained and almost unexamined curiosity until it was considered around i960 
by the Soviet astrophysicist I. S. Shklovskii. Shklovskii considered a wide range of 
alternative hypotheses for the secular acceleration, among them the influence of 
the Sun, the influence of a hypothetical magnetic field on Mars, and the tidal 
influence of the gravity of Mars. He found that none of these came close to 
working. He then reconsidered the possibility of atmospheric drag. The exact size 
of the Martian satellites was known poorly and indirectly in those days before 
spacecraft investigation of Mars, but it was known that Phobos was roughly ten 
miles in diameter. The altitude of Phobos above the surface of Mars was also 
known. Shklovskii and others before him found that the density of the atmosphere 
was far too low to produce the drag that Sharpless had deduced. It was at this 
point that Shklovskii made a brilliant and daring guess. 

All the calculations showing atmospheric drag to be ineffectual had assumed 
that Phobos was an object of ordinary density. But what if its density were very 
low? Despite its enormous size, its mass would then be quite small, and its orbit 
could be appropriately affected by the thin upper atmosphere of Mars. 

Shklovskii calculated the required density of Phobos, and found a value about 
one one-thousandth the density of water. There is no natural object or substance 
with such low density; balsa wood, for example, has about half the density of 
water. With such a low density, there was only one conclusion possible: Phobos 
had to be hollow. A vast hollow object ten miles across could not have arisen by 
natural processes. Shklovskii, therefore, concluded that it was produced by an 
advanced Martian civilization. Indeed, an artificial satellite ten miles across 
requires a technology far in advance of our own; it would also be far in advance of 


the technology imagined on Barsoom by Burroughs, which was a kind of sword 
and small spaceship technology. 

Since there were no signs of such an advanced civilization on Mars today, 
Shklovskii concluded that Phobos - and possibly Deimos — had been launched in 
the distant past by a now extinct Martian civilization. (The interested reader may 
find more details of this remarkable argument of Shklovskii's in the book 
Intelligent Life in the Universe, jointly authored by Shklovskii and myself. [San 
Francisco, Holden-Day, 1966; New York, Delta Books, 1967]). Subsequent to 
Shklovskii's first work on the subject, the motions of the moons of Mars were re- 
examined in England by G. A. Wilkins, who found that possibly there was no 
secular acceleration. But he could not be sure. 

Shklovskii's extraordinary suggestion that the moons of Mars might be artificial 
is one of three hypotheses on their origin. The other two - certainly interesting in 
their own right, but naturally paling in comparison with the Shklovskii hypothesis 
— are (1) that the moons are captured asteroids, or (2) that they are debris left over 
from the origin of Mars itself. 

Asteroids are hunks of rock and metal that go around the Sun between the 
orbits of Mars and Jupiter. There are unlikely, but theoretically possible, scenarios 
in which the gravitation of Mars can capture a close-passing asteroid. 

In the Martian-debris hypothesis, it is imagined that pieces of rock of various 
sizes fell together to form Mars; that the last generation of such infalling pieces 
produced the large old impact craters on Mars (see page 131); and that Phobos and 
Deimos are by chance the only remnants still extant of the early catastrophic 
history of Mars. 

It is clear that establishing any one of these three hypotheses on the origin of 
the moons of Mars would be a major scientific achievement. 

The Mariner Mars mission of 1971, which I had the pleasure to work on, was 
originally to have involved two spacecraft, Mariner 8 and Mariner 9. They were to 
be placed in different orbits for different purposes in the study of Mars itself. 
After these orbits were finally agreed upon, I noticed that they were not all that 
far from the orbits of Phobos and Deimos. It also seemed to me that television and 
other close-up observations of Phobos and Deimos by the Mariner spacecraft 
might permit us to determine something of their origin and nature. 

I therefore approached officials of NASA, which organized and ran the 
mission, for permission to program observations of Phobos and Deimos. While the 
mission controllers at Jet Propulsion Laboratory, the actual operating organization, 
were not unsympathetic to this idea, some officials at NASA headquarters were 
against it. There was a mission plan, written in a large book, which stated what 
Mariners 8 and 9 were about. Nowhere in the mission plan were Phobos and 
Deimos mentioned. Ergo, I could not look at Phobos and Deimos. 

I pointed out that my proposal required only moving the scan platforms on the 
spacecraft so that the cameras could observe the Martian satellites. The response 
was negative again. A short time later, I advanced the argument that if Phobos and 


Deimos were indeed captured asteroids, examining them from Mariner g was the 
equivalent of a free mission to the asteroid belt: The proposed scan platform 
maneuver would save NASA two hundred million dollars or so. This argument 
was judged, at least in some circles, to be more compelling. After about a year of 
my lobbying, a planning group on satellite astronomy was set up, and tentative 
plans were made for examining Phobos and Deimos. The satellite astronomy 
working group was, at my suggestion, chaired by Dr. James Pollack, a former 
student of mine; but it was a sign of NASA reluctance that the group was formed 
only after the launch of Mariner 9, and only about two months before its arrival at 
Mars. [Mariner 8 had, meanwhile, failed.) 

When Mariner 9 arrived at Mars, we found a planet almost entirely obscured 
by dust. Since there was little to look at on Mars, a great and previously 
undetectable enthusiasm for examining Phobos and Deimos dramatically 
materialized. The first step was to take wide-angle photographs from a distance in 
order to establish with some precision the orbits and locations of the moons. This 
task was accomplished in a preliminary way about two weeks after injection of 
the spacecraft into Martian orbit. Mariner 9 has an orbital period of about twelve 
hours, so that it made close to two revolutions around Mars per day. 

The television pictures from Mariner 9 were radioed from Mars to Earth in 
much the same way that a newsprint wire-photo is transmitted on Earth. The 
picture is divided into a large number of small dots (for Mariner 9, several 
hundred thousand dots), each dot with its own brightness, or shade of gray, 
running from black to white. After the picture is taken by the spacecraft and 
recorded there on magnetic tape, it is played back to Earth, dot by dot. The 
communication says, in effect: Dot number 3277, gray level 65; dot number 3278, 
gray level 62, and so on. The picture is reassembled by computer on the Earth - 
essentially by following the dots. 

The first moderately close-up photograph of Phobos was obtained on 
revolution 31. Page 100 shows a Polaroid photo of the video-monitor image of 
Phobos on revolution 31, received on November 30, 1971. The image is much too 
indistinct to make any conclusions whatever. 


The first Mariner 9 image of Phobos, unprocessed by com- 
puter, (See also photos on pages 102 and 103.) 

Late that same night, Dr. Joseph Veverka, of Cornell, another former student 
of mine, and I worked into the small hours of the morning at the Image Processing 
Laboratory of JPL to bring out - by computer contrast-enhancement techniques - 
all of the detail present in the image. The result is shown on page 102. The shape is 
irregular. Are those blotches craters? 


The same photograph as on page 100, contrast-enhanced 
by computer, and showing cratering. 

Our computer-enhanced photograph was constructed on the computer's video 
monitor, line by line, from top to bottom. As the apparent large crater at the top 
gradually emerged, we saw a single bright spot at its center; for just a moment, I 
had the sense that we were seeing a star through an enormous hole in Phobos - or, 
even more chilling, that we were seeing an artificial light. But when we requested 
the computer to remove all single-bit errors, the bright spot went away. 

On revolution 34, Mariner 9 and Phobos came within less than four thousand 
miles of each other, one of the closest approaches in the entire mission. Late on 
the night of the receipt of that picture, Veverka and I were again computer- 
enhancing. Our results were like those seen on the accompanying page 103. I am 
not sure what an artificial satellite ten miles across looks like, but this does not 
seem to be it. Phobos looks not so much like an artificial satellite as a diseased 
potato. It is, in fact, very heavily cratered. For it to have accumulated so many 
craters in that part of the Solar System, it must be very old, probably billions of 
years old. 


A later, much more detailed image of Phobos showing its 
true nature. 

Phobos appears to be an entirely natural fragment of a larger rock severely 
battered by repeated collisions; holes have been dug, pieces have been chipped off. 
It looks a little like the hand axes, chipped along natural fracture planes, made by 
our Pleistocene ancestors. There is no sign of technology on it. Phobos is not an 
artificial satellite. When pictures of Deimos were computer contrast-enhanced, 
the same conclusion applied to it. 

Phobos and Deimos are the first satellites of another planet to have been 
photographed close-up. They were also observed by the ultraviolet spectrometer 
and the infrared radiometer on board Mariner g. We have been able to determine 
their sizes and shapes and something of their color. They are extremely dark 
objects - darker than the darkest material that is likely to be in the room in which 
you are sitting right now. 

Indeed, they are among the very darkest objects in the Solar System. Since 
there are so few objects this dark anywhere, we hope to be able to conclude 
something about their composition. They are both covered by at least thin layers 
of finely pulverized material. They provide important clues to collisional processes 
in the early Solar System. I believe we are looking at the end-product of a kind of 


collisional natural selection, in which fragments have been broken off from a larger 
parent body, and we are seeing only the two pieces, Phobos and Deimos, that 
remain. The moons of Mars are also important collision calibrators for Mars. 
Phobos, Deimos, and Mars have very likely been together in the same part of the 
Solar System for a very long period of time. The number of craters of a given size 
on Mars is much less, in general, than on Phobos and Deimos, providing important 
information on erosional processes that exist on Mars and that do not exist on 
airless and waterless Phobos and Deimos. 

Because we now have the first good information on the size and shape of these 
objects, and because we now have good reason to think that they have typical 
densities of ordinary rock, we can calculate something about what it would be like 
to stand on, let's say, Phobos. First of all, Mars, less than six thousand miles away, 
would fill about half the sky of Phobos. Marsrise would be a spectacular event. 
Eventual construction of an observatory on Phobos to examine Mars might not be 
such a bad idea. We know from Mariner 9 that both Phobos and Deimos are 
rotating as our Moon does, always keeping the same face to their planet. When 
Phobos is above the day hemisphere of Mars, the reddish light of Mars would be 
enough to read by at night on Phobos. 

Because of their small sizes, Phobos and Deimos have very low gravitational 
accelerations. Their gravities do not pull very hard. The pull on Phobos is only 
about one one-thousandth of that on Earth. If you can perform a standing high 
jump of two or three feet on Earth, you could perform a standing high jump of 
half a mile on Phobos. It would not take many such jumps to circumnavigate 
Phobos. They would be graceful, slow, arcing leaps, taking many minutes to reach 
the high point of the self-propelled trajectory and then to return gently to the 

Even more interesting would be a game like baseball on Phobos. The velocity 
necessary to launch an object into orbit about Phobos is only about twenty miles 
per hour. An amateur baseball pitcher could easily launch a baseball into orbit 
around Phobos. The escape velocity from Phobos is only about thirty miles per 
hour, a speed easily reached by professional baseball pitchers. A baseball that had 
escaped from Phobos would still be in orbit about Mars — a man-launched 
moonlet. If Phobos were perfectly spherical, a lonely astronaut with an interest in 
baseball could invent a curious but somewhat sluggish version of this already 
rather sluggish game. First, as pitcher, he could throw the ball sidearm — at the 
horizon at between twenty and thirty miles per hour. He could then go home for 
lunch, because it will take about two hours for the baseball to circumnavigate 
Phobos. After lunch, he can pick up a bat, face the other direction and await his 
pitch of two hours earlier. Apart from the fact that good pitchers are seldom good 
hitters, hitting this pitch would be pretty easy: About fifteen seconds elapse from 
the appearance of the baseball at the horizon to its arrival in the vicinity of our 
astronaut. If he swings and misses - or, more likely, if the ball is wide of the plate 
- he can then go home for a two-hour nap, returning with his catcher's mitt to 


catch the ball. Alternatively, if he succeeds in hitting a fly ball at a velocity 
somewhere between twenty and thirty miles per hour, he can go home and take 
his nap, returning this time with a fielder's mitt, awaiting the return of the ball 
from the opposite horizon two hours later. Because Phobos is gravitationally 
lumpy, the game would be more difficult than I have indicated. Since daylight on 
Phobos lasts only about four hours, lights would have to be erected, or the game 
modified so that all pitching, hitting, and catching events happen on the day side. 

These sports possibilities may, one day a century or two hence, provide a 
tourist industry for Phobos and Deimos. But baseball on Phobos is no more an 
argument for going there than, to take a random example, golf is for going to the 
Moon. The scientific interest in the moons of Mars - whether captured asteroids 
or debris from the formation of the planet - is, however, immense. Sooner or later, 
certainly on a time scale of centuries, there will be instruments — and then men - 
on the surface of Phobos looking up with awe at an immense red planet that fills 
the sky from zenith to horizon. 

And what about the opposite view? What do the moons of Barsoom look like 
from the surface of Mars? Because Phobos is so close to Mars, it would be seen as a 
clearly discernible disc, even though it is intrinsically such a tiny object. In fact, 
Phobos would appear as about half the apparent size of our Moon seen from the 
surface of Earth. We have found from Mariner g that only one side of Phobos is 
visible from Mars, just as only one side of our Moon is visible from Earth. That 
face of Phobos is, more or less, the face on page 102. Until Mariner 9, no one — 
except Martians, if such there be - ever knew that face. 

Because Phobos is so close to Mars, Kepler's laws constrain it to move 
comparatively rapidly about the planet. It makes approximately 2V2 revolutions 
about Mars in 24 hours. Deimos, on the other hand, takes 30 hours 18 minutes to 
revolve in its orbit once about Mars. Both moons revolve in their orbits in the 
same direction or sense as Mars rotates on its axis. Thus, Deimos rises in the east 
and sets in the west as - from terrestrial chauvinism - we believe a well-behaved 
satellite should. But Phobos makes it once around its orbit in less time than it 
takes for Mars to rotate. Accordingly, Phobos rises in the west and sets in the east, 
taking about 5V2 hours to transit from horizon to horizon. This is not exactly 
"hurtling" — the motion would not be easily perceptible against the field of stars in 
a minute's watching — but it's not plodding, either. There will be some nights at 
the equator on Mars when Phobos sets in the east at sunset and then rises in the 
west well before dawn. 

Phobos is so close to the equatorial plane of Mars that it is entirely invisible 
from the polar regions of the planet. If we were to imagine intelligent beings 
developing on Mars, astronomy might very well be the province of only the 
equatorial, and not the high- latitude, societies. I am not sure whether Helium was 
an equatorial kingdom. 

Freud says somewhere that the only happy men are those whose boyhood 
dreams are realized. I cannot say that it has made my life carefree. But I will never 


forget those early-morning hours in a chilly California November when Joe 
V everka, a JPL technician, and I were the first human beings ever to see the face 
of Phobos. 

The State of California was kind enough to give me an automobile license plate 
marked "PHOBOS." My car is not particularly sluggish, but it cannot 
circumnavigate our planet twice a day, either. The license plate pleases me. I 
would have preferred "BARSOOM," but there is a strictly enforced limit of six 
letters per license plate. 


Topographical map, baaed on radar studies, of elevations at 
mid latitudes on Mars. Laboratory for Planetary Studies, Cor- 
nell University. 


i6. The Mountains of Mars 

I. Observations From Earth 

The mountains of the Earth are the product of ages of geological catastrophes. 
The major folded mountain ranges are thought to be produced by the collision of 
enormous continental blocks during continental drift The motion of continents 
toward and away from each other, at a rate of about an inch a year, seems terribly 
slow to us. But since the Earth is billions of years old, there has been plenty of 
time for continents to bang around all over our planet. 

Lesser mountains were produced by volcanic events. Hot molten rock, called 
lava, upwells through tubes in the upper layers of the Earth - tubes of structural 
weakness through which the underlying pressure is relieved - and produces large 
surface piles of cooling volcanic slag. The resulting hole in the top of the volcanic 
mountain — the geologists call it a summit caldera - is the channel through which 
successive episodes of lava-upwelling occur. In the summit caldera of an active 
volcano, as, for example, in Hawaii, we can actually see molten lava. These 
individual volcanic mountains and mountain ranges, which are not really separate 
entities, are signs of a geologically vigorous and dynamic Earth. 

What about Mars? It is a smaller planet than Earth; its central pressures and 
temperatures are less; it has a lower average density than Earth. These 
circumstances combine to suggest that Mars should be geologically less active than 
Earth, perhaps like the Moon. But even on the Moon, a much smaller object than 
Mars, with even lower anticipated interior temperatures than Mars, recent signs of 
volcanic activity have been uncovered by the Apollo missions. We do not even 
today understand the connection between the size and structure of a planet and 
the presence of volcanism and mountains, although we do know that there are no 
significant folded mountain ranges on the Moon. 

Our present ignorance on this subject is exceeded by the ignorance of the early 
planetary astronomers, less than a century ago, as they peered through small 
telescopes and tried to guess what distant Mars was like. One of the earliest 
astronomers to commit himself on the question of mountains on Mars was 
Percival Lowell. Lowell believed (see Chapter 18) that he had found evidence of 
an extensive network of straight lines, crisscrossing the Martian surface with 
remarkable regularity and straightness, and that could only have been produced by 
a race of intelligent beings on that planet. He believed that these "canals" were 
truly canals carrying water. We now know that the problem was not so much 
with his logic as with his observations; none of the Mariner or other recent 
quantitative observations of Mars have shown any sign of the Lowellian canals. 

In the 1890s Lowell argued that Mars must have no mountains, because 
mountains would be a severe impediment to the construction of a comprehensive 
network of canals. But surely a race that could construct a planet-wide network of 


canals should be able now and again to mow down an awkwardly placed 

Nevertheless, Lowell was among the very first astronomers to apply an actual 
observational test to the question of mountains on Mars. He looked beyond the 
terminator. The terminator is the line — sharp or fuzzy, depending on the absence 
or presence of a planetary atmosphere - that separates the day from the night side 
of a planet. The terminator moves around the planet once a day - the local 
planetary day. But if there are mountains just on the night side of the terminator, 
the mountains will receive the rays of the setting Sun when their adjacent valleys 
are in darkness. Galileo first used this technique to discover what he called the 
mountains of the Moon - although the lunar mountains are mainly enormous 
pieces of rubble that fell out of the sky in the final phases of the formation of the 
Moon, rather than mountains of the terrestrial type, produced by a geologically 
active interior. 

Lowell and his collaborators found cases of bright projections beyond the 
Martian terminator, illuminated by the rays of the setting Sun. But when they 
calculated their altitudes - an easy task for anyone grounded in high school 
geometry - the mountains were found to be many tens of miles high. Such 
elevations on Mars seemed to him absurd because of his canal argument. 
Moreover, the next day — the day on Mars is almost exactly the same length as a 
day on Earth — when the feature was seen again, its position had changed. This 
behavior is quite uncharacteristic of mountains of whatever origin, and Lowell 
correctly concluded that he had been seeing dust storms, in which fine particles 
from the Martian surface had been carried some tens of miles into the Martian 

Such dust storms are also observed when we examine through the telescope 
the day side of Mars. We sometimes see that the characteristic configuration of 
bright and dark markings on the planet is temporarily obscured. There is an 
intrusion of bright-area material into the dark area, followed by a reappearance of 
the former configuration. These changes were interpreted in Lowell's time as dust 
storms arising in the bright areas and obscuring the adjacent dark areas. The 
present interpretation, based on the full range of Mariner g close-up observations, 
confirms this view (see Chapter 1 9) . 

Lowell and his contemporaries called the bright areas "deserts," and this, too, 
seems to be an appropriate name. The Lowellians concerned themselves with the 
problem of whether bright areas tended to be higher or lower than dark areas, 
even though the elevation difference was expected to be extremely small. A dark 
area seen at the illuminated limb, or edge, of the planet seemed to be a notch or 
depression. But this could be understood merely in terms of the darkness of the 
dark area: If it were dark against a dark sky, we would not see it at all. We might 
gain the mistaken impression of a notch or depression. The prevailing opinion of 
most astronomers seems to have been that the dark areas were slightly lower than 
the bright, but the difference was estimated by Lowell as only half a mile or less. 


In 1966, I re-examined this problem with Dr. James Pollack. We used two 
main arguments. Mars has in its winter hemisphere a large polar cap which, at 
various times, has been ascribed to frozen water or frozen carbon dioxide. Even at 
the present time its composition is unsettled; both substances are probably 
present. As the polar cap retreats in each hemisphere, once each year, there are 
regions where frost is left behind. Later, when the frost leaves these regions, they 
are found to be brighter than their surroundings. By analogy with the Earth, we 
might expect them to be high mountainous regions that remain frosted after the 
snows of the valleys have melted or evaporated. Indeed, one Martian polar region 
- the so-called Mountains of Mitchel - was identified as mountainous by this 
argument alone. 

But why are terrestrial mountains the last places to be frost-free? Because it is 
colder as we walk uphill, as every mountaineer knows. But why does it get colder 
as we walk uphill? Do the reasons that make terrestrial mountaintops colder than 
their bases apply to Mars? 

We concluded that all factors that make it colder while walking uphill on the 
Earth are inoperative on Mars, mainly because of the very thin Martian 
atmosphere. But the winds on Mars should be higher at mountaintops than in 
valleys, as on Earth. This is not a conclusion from analogy, but is based on the 
appropriate physics. Therefore, we imagined that snows are removed by high 
winds preferentially from the mountains of Mars, and that the bright areas that 
retain frost on Mars are, therefore, low. 

Our second line of attack was based on the radar observations of Mars, which 
began in the middle 1960s. There was one piece of evidence that immediately 
caught our attention. When the small central part of the radar beam was 
positioned directly on a dark area of Mars, only a very small fraction of the radar 
signal was returned to Earth. But when an adjacent bright area, on one side or the 
other of this dark region, was under the center of the radar beam, the reflection 
was much stronger. This could be understood if the dark area were either much 
higher or much lower than the adjacent bright area. From the preliminary radar 
evidence then available, we concluded that if it had to be one or the other of these 
two alternatives, the dark areas had to be systematically high on Mars. We 
concluded that major elevation differences existed on Mars, in some cases as much 
as ten miles between adjacent bright and dark areas. The large-scale slopes were at 
most only a few degrees - not a very steep grade — and both the elevation 
differences and slopes were comparable to those on Earth, although the elevations 
seemed to be greater than here. The notion that the deserts generally were 
lowlands seemed consistent with the notion of fine sand and dust being trapped in 
low valleys, with the tops of mountains - where the winds are higher - being 
scoured of small, bright, fine particles. 

In the few years following our analysis many more detailed radar studies were 
done - principally by a group at the Haystack Observatory of the Massachusetts 
Institute of Technology, headed by Professor Gordon Pettengill. For the first time 


it was possible to do direct radar altitude measurements. Instead of using our 
indirect arguments, the technology had reached a point where it was possible to 
measure how long it took the radar signal to reach Mars and be returned from it. 
Those places on Mars from which the radar signal took longest to return were 
farthest from us, and, therefore, deepest. Those regions from which the radar 
signal took the least time to return were closer to us, and, therefore, highest. In 
this way the first topographic maps of selected regions of the Martian surface were 
constructed. The maximum elevation differences and slopes were just about what 
we had concluded by much more indirect means. 

But dark areas did not appear to be systematically higher than bright areas. 
Pettengill and his colleagues found that a bright region of Mars called Tharsis 
appeared to be very high - perhaps the highest region sampled on the planet. A 
major Martian bright circular area called Hellas - Greek for "Greece" - indeed 
turned out to be very low from later nonradar observations. A somewhat similar 
feature called Elysium, also large and bright and roughly circular, turned out to be 
high. The darkest big Martian area, Syrtis Major, turned out to be a steep slope. 

Why were Pollack and I only partly right? Because of Occam's Razor, a 
convenient and frequently used principle in science, but one that is not infallible. 
Occam's Razor recommends that, when faced with two equally good hypotheses, 
we choose the simpler. We had assumed that dark areas were either systematically 
high or systematically low. If that were the case, dark areas would have to be 
systematically high. But that is not the case; dark areas can be either high or low. 
Our conclusions only reflected our assumptions. 

But I am very pleased that we were able, through logic and physics, to get the 
story at least partly right, and to demonstrate that there are enormous elevation 
differences on Mars, elevations much vaster than Lowell had expected. I find it 
more difficult, but also much more fun, to get the right answer by indirect 
reasoning and before all the evidence is in. It's what a theoretician does in science. 
But the conclusions drawn in this way are obviously more risky than those drawn 
by direct measurement, and most scientists withhold judgment until there is more 
direct evidence available. The principal function of such detective work — apart 
from entertaining the theoretician - is probably to so annoy and enrage the 
observationalists that they are forced, in a fury of disbelief, to perform the critical 


Martrur 9 mosaic of four photographs of the largest known 
volcano in solar system. Nix Olympica-seen vertically from 
above. Courtesy. NASA. 


\-j. The Mountains of Mars 

II. Observations From Space 

The epic flight of Mariner g to Mars in 1971 produced a new set of definitive and 
direct measurements concerning the mountains and elevations of Mars. 
Moderately complete elevation terrain maps of Mars have been developed as a 
result of the ultraviolet spectrometer, the infrared interferometric spectrometer, 
and the S-band occultation experiments aboard Mariner g. But the most striking 
information on the mountains of Mars came from the television experiment. 

The first pictures that Mariner g returned from Mars, obtained even before 
orbital insertion on November 14, 1971, showed an almost completely featureless 
planet. The south polar cap could be discerned dimly, but the bright and dark 
markings, which had been seen and debated for over a century, were nowhere to 
be found. This was not a failure of the television camera, but rather the result of a 
spectacular planet-wide dust storm, which had begun in late September and 
would not significantly subside until early January. 

The earliest pre-orbital pictures and the first few days of orbital pictures 
showed no significant nonpolar detail - except in the region of Tharsis. Here, there 
were four dark, somewhat irregular spots to be seen, three of them in an 
approximate straight line running northeast to southwest; the fourth was isolated 
away from them and to the west. Since there was otherwise nothing much visible 
on the planet, I devoted some attention to these spots in the early phases of the 
mission - so much attention that for a while they were known as "Carl's Marks" 
by several of my wittier co-investigators. I, in turn, proposed naming them Harpo, 
Groucho, Chico, and Zeppo, but this was all before their significance was 

The isolated spot corresponded in position quite well with the classical Martian 
feature named Nix Olympica - Greek for the Snows of Olympus, the home of the 
gods. The other three spots seemed to correspond to no familiar Martian surface 
features. But Bradford Smith, astronomer at New Mexico State University, 
pointed out that they corresponded quite well (as did Nix Olympica) to places on 
Mars that exhibited local afternoon brightening as observed from Earth. In some of 
Smith's ground-based telescopic photographs, obtained with a blue or violet filter 
and when there was no dust storm on Mars, these four places appeared as brilliant 
white spots, even though the contrast between the usual bright and dark areas was 
very small and the usual markings of Mars were indiscernible (the usual situation 
when Mars is viewed in blue or violet light rather than in orange or red light). 
Were we observing some sort of dark clouds in the midst of the dust storm at sites 
where bright clouds were usually found? 

Another Mariner g experimenter, William Hartmann of Science Applications, 
Inc., Tucson, Arizona, performed a computer contrast-enhancement of the original 
photographs of the four spots and found some faint indication of circular central 


regions in at least two of them. Indeed, the Mariner 6 and 7 photographs of Nix 
Olympica, taken in 1969, showed a similar indication there. 

By this time, the extent and severity of the dust storm had become evident, 
and part of our preplanned mission for Mariner 9 to map the planet had to be 
postponed. This then freed a significant picture-taking ability for high- resolution, 
close-up photographs of the four spots. These experiments of opportunity were 
possible only because Mariner 9 had a major adaptive capability. The scan 
platform, on which the cameras were located, could be aimed at many desired 
spots on Mars, and the technical staff of the Jet Propulsion Laboratory of the 
California Institute of Technology was able to change its plans quickly enough to 
accommodate the changed scientific needs of the mission. Because of the design of 
the spacecraft and the adaptability of its controllers, the first close-up photographs 
of the four spots began coming in. 

Each spot had a vaguely circular center. There were parallel arcuate segments. 
There was a kind of scalloping. All these features were dark against a bright 
surrounding, corresponding to the dark appearance of the spots as seen initially in 
low resolution. 

The particular shapes that we had seen in the early pictures held no particular 
significance for me. But I was struck by the fact that these circular features 
occurred in Tharsis, the highest region on Mars. These features were craters. Why 
were we seeing them and virtually no other Martian features? Because they must 
be the highest regions in Tharsis, a region already enormously elevated. The four 
spots, therefore, seemed to me to be vast mountains poking through the dust. I 
proposed that as time went on and the dust storm settled (from experience with 
other Martian global dust storms over decades of observation, we knew the dust 
storms would have to settle eventually), we would see more and more of these 
mountains, clear down to their bases. I even thought it possible that we could 
produce topographic maps from the sequence of emerging detail as the dust 
settled. Unfortunately, the settling out of the dust was a very irregular affair, and 
this suggestion has not yet borne fruit. 

Geologist members of the Mariner 9 television team, such as Harold Masursky 
and John McCauley, of the U. S. Geological Survey, were taken with the form of 
the craters, and quite early identified them - by analogy with similar features on 
Earth - as vast volcanic piles with summit calderas. I have always been mistrustful 
of arguments from terrestrial analogy. After all, Mars is quite another place. For all 
we knew - at least, for all I knew - quite different geological processes might 
operate there, and Earth-like features might be produced by different causes. 

However, by another route I reached the same conclusion as the geologists: 
There are only two processes we know that produce craters - the impact of 
interplanetary debris (the origin, for example, of most of the craters on the Moon) 
and vulcanism. It would be asking too much to expect that the large meteorites or 
small asteroids that carved out four of the largest impact craters in Tharsis knew 
enough to land on the top of the four highest mountains in Tharsis. Much more 


plausible is the idea that the mechanism that made the mountain made the crater. 
That mechanism is called vulcanism. 

As the dust storm cleared, the true magnitude of these four volcanic mountains 
became clear. The largest of them, Nix Olympica, is five hundred miles across, 
larger than the largest such feature on the Earth, the Hawaiian Islands. The 
altitudes of the spots have not yet been determined with precision, but they 
appear to be ten to twenty miles above the mean level of the planet. (We cannot 
talk of sea level on Mars because there are not - today, at any rate - any seas 
there.) Over a dozen smaller volcanoes have since been found in other regions of 

The infrared radiometer on Mariner g showed no sign of hot lava in the 
summit calderas of the craters. On the other hand, their fresh appearance and the 
almost total absence of meteorite cratering on their slopes show them to be very 
young objects, geologically speaking — probably no more than a few hundred 
million years old, possibly younger. 

The association of clouds with these volcanic mountains could be due to 
contemporary outgassing from the calderas - steam, for example, being exhaled up 
volcanic vents. But it seems more likely that the clouds are present at the summits 
of these mountains precisely because these mountains are so high. An imaginary 
parcel of Martian air, rising along the slope of the mountain, expands and cools. 
(The air gets colder as we go upward in the Martian atmosphere. But because the 
air is so thin on Mars, it cannot exchange heat well with the surface; thus the 
surface does not get cold as we go uphill on Mars, as we discussed earlier.) When 
the temperature in the parcel of air drops below the freezing point of water, all of 
the water vapor in the parcel condenses out into ice crystals. The amount of water 
vapor we know to exist in the Martian atmosphere, the heights of the mountains, 
and the amount of small ice crystals necessary to produce a visible cloud together 
work out correctly for this to be the explanation of mountain clouds on Mars. 

Recent vulcanism on Mars implies outgassing, whether or not the clouds that 
we see at the summits of these volcanoes are signs of outgassing. When hot lava 
flows to the surface, it carries with it a significant amount of gas — on the Earth, 
mainly water, but with a significant amount of other materials. Thus, the 
volcanoes that we see on Mars must have made an important contribution to the 
Martian atmosphere. In part, at least, the air has come out of these holes in the 
ground. Because Mars is so cold today, water can be trapped in many forms, such 
as ice, and not remain in the atmosphere. Much more gas could have been 
produced by these volcanoes than we see in the Martian atmosphere today. If 
there is life on Mars, it will almost surely be based on the exchange of material 
with the atmosphere - just as on Earth, where the cycle of green-plant 
photosynthesis and animal respiration is predominant. If there is life on Mars, 
these volcanoes may - at least indirectly — have played an important role in its 
present development. 


After the dust storm cleared, Mariner 9 was moved into a higher orbit, to 
facilitate the geological mapping originally planned. The spacecraft worked many 
times longer than its designers had expected. Complete geological coverage of the 
planet has been accomplished down to a resolution of half a mile. The resulting 
geological maps reveal an enormous array of linear ridges and grooves that 
surround the Tharsis Plateau - as if a third or a quarter of the whole surface of 
Mars were cracked in some colossal recent event that lifted Tharsis. The most 
spectacular of these quasilinear features is an enormous rift valley in a region called 
Coprates. It runs 80 degrees of Martian longitude and is almost exactly as long as 
the largest rift valley on the Earth, the East African Rift V alley, which runs up the 
entire east coast of Africa to the Dead Sea. Since Mars is a smaller planet, the 
Coprates Rift V alley is, relatively speaking, a much more impressive feature. 

The East African Rift Valley occurs because of sea floor spreading and 
continental drift. The African and Asian continents are slowly moving away from 
each other, and the chasm that is developing there is the East African Rift Valley. 
But continental drift is thought to be due to the slow circulation of material in the 
mantle of the Earth. Should we then conclude that Mars, despite its smaller size 
and lower internal temperatures, also has mantle convection and continental drift? 
Or is it possible that different processes produce similar features on the two 

Whatever the answer, we cannot help but learn a great deal more about the 
old Earth-bound science of geology - with its practical future disciplines, such as 
earthquake prediction and control - by examining the geology of our neighboring 
planet Mars. 



A sinuous channel on Mors— probably carved by an ancient 
river. Courtesy, NASA. 


18. The Canals of Mars 

In 1877 (as in 1971) the planet Mars was close - forty million miles from Earth. 
European astronomers, with newly developed telescopes, prepared for what was 
then Man's most detailed look at our planetary neighbor. One of them was 
Giovanni Schiaparelli, an Italian observing in Milan and a collateral relative of the 
present couturier and perfume enterpriser. 

Generally speaking, the telescopic view of Mars was blurred and fuzzy, 
interrupted by the variable turbulence in the Earth's atmosphere that astronomers 
call "seeing." But there were moments when the Earth's atmosphere steadied and 
the true detail on the disc of Mars seemed to flash out. Schiaparelli was astonished 
to see a network of fine straight lines covering the disc of Mars. He called these 
lines canali, which in Italian means "channels." However, canali was translated 
into English as "canals," a word with a clear imputation of design. 

Schiaparelli's observations were taken up by Percival Lowell, a diplomat once 
posted in Chosen, the present Korea. A Boston Brahmin, the brother of the 
president of Harvard University and of an even more famous personage, the 
poetess Amy Lowell (for some reason renowned for smoking little black cigars), 
Lowell established a private observatory in Flagstaff, Arizona, to study the planet 
Mars. He found the same canali that Schiaparelli had. He extended their 
description and elaborated an explanation. 

Mars was, Lowell concluded, a dying world on which intelligent life had arisen 
and accommodated itself to the perils of the planet. The chief peril was the dearth 
of water. The Martian civilization, Lowell imagined, had constructed an extensive 
network of canals to carry water from the melting polar caps to the habitations in 
more equatorial climes. The turning point of the argument was the straightness of 
the canals, some of them following great circles for thousands of miles. Such 
geometrical configurations, Lowell thought, could not be produced by geological 
processes. The lines were too straight. They could only have been produced by 

This is a conclusion with which we all can agree. The only debate is about 
which side of the telescope the intelligence was on. Lowell believed that the 
penchant for Euclidian geometry was on the distant end of the telescope. But the 
difficulties in drawing a great deal of mottled fine detail in a few seconds of good 
seeing are so great that the eye-brain-hand combination is sorely tempted to 
connect such disconnected features into straight lines. Many of the best visual 
astronomers observing Mars between the turn of the century and the dawn of the 
space age found that, while they could see canals under conditions of good but not 
superb seeing, they were able in the extremely rare moments of perfect seeing to 
resolve the straight lines into a multitude of spots and irregular detail. 

Then it was found that at least the vast bulk of the polar caps are carbon 
dioxide and not frozen water. The atmospheric pressure was discovered to be 


much less than on Earth. Liquid water was found to be entirely impossible. The 
idea of advanced forms of life and canals on Mars died. And yet . . . 

As the planet-wide dust storm cleared in 1971, the Mariner 9 spacecraft began 
to photograph a region called Coprates by the classical observers. Coprates was 
one of the largest canali found by Lowell, Schiaparelli, and their followers. 
Toward the end of the dust storm, Coprates was revealed to be an enormous rift 
valley running three thousand miles east to west near the Martian equator, fifty 
miles wide in spots and a mile deep. It was not perfectly straight - it was certainly 
not an engineering work; but it was a vast gash proportionately longer than any 
such feature on Earth. 

And running out of Coprates were features that were very curious indeed - 
sinuous channels, meandering through the highlands above the Coprates Valley 
and graced with beautiful little tributaries. If such channels had been seen on 
Earth, they would unhesitatingly have been attributed to running water. But on 
Mars the surface pressures are so low that liquid water would instantly vaporize, 
just as the pressures on Earth are so low that liquid carbon dioxide vaporizes 
instantly. On Earth we have solid carbon dioxide and gaseous carbon dioxide, but 
not liquid carbon dioxide. On Mars this absence of the liquid phase is true as well 
for water. 

But as the Mariner 9 photographic mission continued, a variety of additional 
channels were discovered: Channels with second- and third-order tributary 
systems, channels without a crater at their beginning or end, channels with 


teardrop-shaped islands in their midst, channels with braided termini, like those 
cut on Earth by episodic flooding. 

There seems to be little doubt that most of the several dozen longest such 
channels (the longest are hundreds of miles long), and hundreds of smaller ones, 
were cut by running water. But since there can be no liquid water on Mars today, 
the channels must have been cut in a previous epoch of Martian history - when 
the total pressures were larger, the temperatures higher, and the availability of 
water greater. 

The channels revealed by Mariner g speak eloquently of the possibility of 
massive climatic change on Mars. In this view, Mars is today in the throes of an ice 
age, but in the past - no one knows just how long ago - it possessed much more 
clement and Earth-like conditions. 

The reasons for such dramatic climatic changes are still being hotly debated. 
Before the Mariner 9 launch, I proposed that such climatic changes leading to 
episodes of liquid water might occur on Mars. They might be driven by the 
precession of the equinoxes, a well-known motion akin to the slow, drifting 
precession of a rapidly spinning top. The precessional periods on Mars are 
something like fifty thousand years. If we are now in a precessional winter, with 
an extensive North polar ice cap, twenty-five thousand years ago may have been 
the precessional winter with an extensive polar ice cap in the South. 

But twelve thousand years ago may have been the epoch of precessional spring 
and summer. The dense atmosphere of that time is now locked away in the polar 
caps. Twelve thousand years ago may have been a time on Mars of balmy 
temperatures, soft nights, and the trickle of liquid water down innumerable 
streams and rivulets, rushing out to join mighty, gushing rivers. Some of these 
rivers would have flowed into the great Coprates Rift V alley. 

If so, twelve thousand years ago was a good time on Mars for life similar to the 
terrestrial sort. If I were an organism on Mars, I might gear my activities to the 
precessional summers and close up shop in the precessional winters - as many 
organisms do on Earth for our much shorter annual winters. I would make spores; 
I would make vegetative forms; I would go into cryptobiotic repose; I would 
hibernate until the long winter had subsided. If this is indeed what Martian 
organisms do, we may be arriving at Mars twelve thousand years too early — or too 

But there is a way to test these ideas. One way the hypothetical Martian 
organisms would know that the precessional spring has arrived is by the 
reappearance of liquid water. Therefore, as Linda Sagan has mentioned, the recipe 
for detecting life on Mars is "Add water." And this is just what the U. S. Viking 
biology experiments, scheduled to land on Mars in 1976 and search for microbes, 
will do. An automatic arm will drop two samples of Martian soil into liquid water. 
A third sample will be inserted into a chamber with no liquid water. If the first 
two experiments give positive biological results, and the third experiment does 


not, some support will be given to this idea that Martian organisms are waiting out 
the long winter. 

But it is entirely possible that the designs of these experiments have been too 
Earth-chauvinist. There may be Martian organisms that enjoy the present 
environment and are drowned in liquid water. The idea of Martian organisms as 
sleeping beauties, awaiting a somewhat wet kiss from Viking, is a long shot - but a 
fascinating one. 

By no means do all of the channels correspond to the positions of the classical 
canali drawn by Lowell and Schiaparelli. Some, like Ceraunius, appear to be 
ridges. Others correspond to no detail that can now be made out. But some, like 
Coprates, are grooves in the Martian terrain. There are channels on Mars. They 
may have biological implications, of a different sort than Lowell imagined (as the 
long- winter model suggests), or they may have no connection with Martian 
biology at all. 

The canals of Lowell do not exist, but the canali of Schiaparelli are there to be 
seen, more or less. One day in the future, perhaps, the channels will again be filled 
with water and, for all we know, with visiting gondoliers from the planet Earth. 


19. The Lost Pictures of Mars 

The Mariner g mission to Mars radioed back to Earth 7,232 photographs that 
revolutionized our knowledge about the planet. Many hundreds of these pictures 
were devoted to studying variable features, the time changes in the relative 
configurations of bright and dark markings on the surface of the planet now 
known to be due largely to wind-blown dust. W e have found thousands of bright 
and dark streaks, beginning in local impact craters and stretching across tens of 
miles of Martian surface. They point in the direction of the prevailing winds. We 
think they are produced by high winds carrying dust out of the craters and 
depositing it on the surface beyond the crater ramparts. These streaks are natural 
wind-direction indicators and, perhaps, anemometers laid down on the Martian 
surface for our edification and delight. We have discovered dark irregular patches 
or splotches, mostly residing in the interiors of craters, which tend to lie on the 
leeward walls of the craters. Thus, the splotches as well as the streaks are wind 
indicators. Some of the splotches have been resolved by Mariner g into enormous 
fields of parallel sand dunes. 

We have discovered many cases of dark streaks and splotches varying through 
the mission in outline or extent. The positions and variabilities of these dark 
features correspond well to the classical dark markings of Mars, observed by 
ground-based astronomers for more than a century and most often attributed by 
them to seasonally changing dark vegetation on the Martian surface. But our 
Mariner g evidence points unambiguously to a meteorological, rather than a 
biological, explanation of the Martian seasonal changes. 

This in no way excludes life on Mars. It merely means that if there is life on 
Mars, it is not easily detectable over interplanetary distances. The same is true in 
reverse: Photographic detection of life on Earth in daylight from the vantage point 
of Mars is impossible, as we have found by studying several thousand orbital 
photographs of our own planet. But the time- varying streaks and splotches on the 
Martian surface are a new and most exciting Martian phenomenon, which cries 
out for further study. 

Since the Martian changes occur slowly, the variable-features objectives 
required very long time intervals between two pictures of the same region to see 
what changes had occurred. At the very end of the mission, fifteen photographs 
were successfully taken by the Mariner 9 cameras of regions in Syrtis Major and 
Tharsis, important for understanding the long-term variations. But when the time 
came to point the high-gain antenna of Mariner 9 to the Earth, so that these 
pictures could be transmitted by playing back the spacecraft's tape recorder, the 
last of the attitude-control gas was used up, Earth-lock could not be acquired, and 
playback did not occur. The spacecraft had literally run out of gas. 

About a year before the Mariner 9 mission was launched, the possibility was 
raised that the spacecraft would run out of control gas. A solution was proposed: 
That the propulsion tanks be connected to the attitude-control gas system - a kind 


of spacecraft anastamosis. Excess propulsion gas could then be used for attitude 
control in case the attitude-control nitrogen was exhausted. This possibility was 
rejected - largely because of its expense. It would have cost $30,000. But no one 
expected Mariner 9 to last long enough to use up its attitude-control gas. Its 
nominal lifetime was ninety days - and it lasted almost a full year. The engineers 
had been overly conservative in assessing their superb product. 

In retrospect, it sounds very much like false economy. With an adequate 
supply of attitude-control gas, the spacecraft might have lasted another full year in 
orbit around Mars. About $150 million of science might have been bought for 
$30,000 of pipe. Had we known that the spacecraft would die from a lack of 
nitrogen, I am almost certain that the planetary scientists involved would have 
raised the $30,000 themselves. 

In fact, there are many such critical junctures in the space program where the 
addition of only a small amount of money can greatly increase the scientific return 
from a given mission. But NA$A, severely limited by funding limitations imposed 
by Congress, the White House, and the Office of Management and Budget, has not 
had such small increments of money. If it were possible, and if a generous donor 
could be found, this would be a superb use for private philanthropy. 

But these are idle musings. No anastamosis was performed; the final playback 
was not accomplished. Bitting there still on the Mariner 9 tape recorder are fifteen 
vital photographs of the planet. They will never be returned under Mariner 9's 
own power. It has now also lost solar lock; sunlight is no longer being converted to 
electricity on its four great solar panels, and there is no way to reactivate it. We 
may never know what Tharsis and $yrtis Major looked like around the beginning 
of November 1972 from the vantage point of Martian orbit. 

Or perhaps we will. Mariner 9 is in an orbit that is slowly decaying in the 
Martian atmosphere. But the decay is so slow that the spacecraft will not crash 
into Mars for another half century. Long before then there should be manned 
orbital flights around Mars. Rendezvous and docking maneuvers are reasonably 
well developed in manned missions even now. Perhaps, then, sometime around 
1990, as a small side-trip in a grand manned-orbital exploration of Mars, there will 
be a rendezvous with Mariner 9. The old and battered spacecraft will be taken 
aboard a large manned station and returned home - perhaps to be put in the 
Smithsonian Institution; perhaps to prevent terrestrial micro-organisms on Mariner 
9 from reaching Mars; but perhaps, also, to rescue and read off the fifteen lost 
pictures of the Mariner 9 mission. 


Three Mariner 9 photographs showing effects of high winds 
near the Martian surface. Above: Wind streaks emanating 
from impact craters. Each streak is a thin layer of wind-blown 
dust. Top right: Splotches in crater interiors. Sonic of these 
features are dark rock exposed when overlying dust is re- 
moved by high winds. Bottom right: Resolution of one of the 
splotches in lop right into an array of longitudinal sand 
dunes, comparable in dimensions to the largest such dune 
fields on Earth. Courtesy. NASA. 



The extremes of climate 
on the Earth. Top- Dune 
field in the Sahara from 
Sahara, C. Kruger, ed.. 
New York, Putnam, 1969. 
Bottom- Crevices in the 
Vatnajokull Glacier in Ice- 
land. from The World 
from Above by O Bihalji- 
Merin. Hill and Wang, 
New York. 1966. 

20. The Ice Age and the Cauldron 

On our tiny planet, spinning in an almost circular orbit at a nearly constant 
distance from our star, the climate varies, sometimes radically, from place to place. 
The Sahara is different from the Antarctic. The Sun's rays fall directly on the 
Sahara and obliquely on the Antarctic, producing a sizable temperature difference. 
Hot air rises near the equator, cold air sinks near the poles - producing 
atmospheric circulation. The motion of the resulting air current is deflected by 
Earth's rotation. 

There is water in the atmosphere, but when it condenses, forming rain or 
snow, heat is released into the atmosphere, which in turn changes the motion of 
the air. 

Ground covered by freshly fallen snow reflects more sunlight back to space 
than when it is snow-free. The ground becomes colder yet. 

When more water vapor or carbon dioxide is put into the atmosphere, infrared 
emission from the surface of the Earth is increasingly blocked. Heat radiation 
cannot escape from this atmospheric greenhouse, and the Earth's temperature 

There is topography on Earth. When wind currents flow over mountains or 
down into valleys, the circulation changes. 

At one point in time on one tiny planet, the weather, as we all know, is 
complex. The climate, at least to some degree, is unpredictable. In the past there 
were more violent climatic fluctuations. Whole species, genera, classes, and 
families of plants and animals were extinguished, probably because of climatic 
fluctuations. One of the most likely explanations of the extinction of the dinosaurs 
is that they were large animals with poor thermoregulatory systems; they were 
unable to burrow, and, therefore, unable to accommodate to a global decline in 

The early evolution of man is closely connected with the emergence of the 
Earth from the vast Pleistocene glaciation. There is an as yet unexplained 
connection between reversals of the Earth's magnetic field and the extinction of 
large numbers of small aquatic animals. 

The reason for these climatic changes is still under serious debate. It may be 
that the amount of light and heat put out by the Sun is variable on time scales of 
tens of thousands or more years. It may be that climatic change is caused by the 
slowly changing direction between the tilt of the Earth's rotational axis and its 
orbit. There may be instabilities connected with the amount of pack ice in the 
Arctic and Antarctic. It may be that volcanoes, pumping large amounts of dust 
into the atmosphere, darken the sky and cool the Earth. It may be that chemical 
reactions reduced the amount of carbon dioxide and other greenhouse molecules 
in the atmosphere, and the Earth cooled. 

There are, in fact, some fifty or sixty different and, for the most part, mutually 
exclusive theories of the ice ages and other major climatic changes on Earth. It is a 


problem of substantial intellectual interest. But it is more than that. An 
understanding of climatic change may have profound practical consequences - 
because Man is influencing the environment of the Earth, often in ways poorly 
thought-out, ill-understood, and for short-term economic profit and individual 
convenience, rather than for the long-term benefit of the inhabitants of the planet. 

Industrial pollution is churning enormous quantities of foreign particulate 
matter into the atmosphere, where they are carried around the globe. The smallest 
particles, injected into the stratosphere, take years to fall out. These particles 
increase the albedo or reflectivity of Earth and diminish the amount of sunlight 
that falls on the surface. On the other hand, the burning of fossil fuels, such as coal 
and oil and gasoline, increases the amount of carbon dioxide in the Earth's 
atmosphere which, because of its significant infrared absorption, can increase the 
temperature of the Earth. 

There is a range of effects pushing and pulling the climate in opposite 
directions. No one fully understands these interactions. While it seems unlikely 
that the amount of pollution currently deemed acceptable can produce a major 
climatic change on Earth, we cannot be absolutely sure. It is a topic worth serious 
and concerted international investigation. 

Space exploration plays an interesting role in testing out theories of climatic 
change. On Mars, for example, there are periodic massive injections of fine dust 
particles into the atmosphere; they take weeks and sometimes months to fall out. 
We know from the Mariner g experience that the temperature structure and 
climate of Mars are severely changed during such dust storms. By studying Mars, 
we may better understand the effects of industrial pollution on Earth. 

Likewise for V enus. Here is a planet that appears to have undergone a runaway 
greenhouse effect. A massive quantity of carbon dioxide and water vapor has been 
put into its atmosphere, so cloaking the surface as to permit little infrared thermal 
emission to escape into space. The greenhouse effect has heated the surface to goo 
degrees F or more. How did this greenhouse-overkill happen on Venus? How do 
we avoid its happening here? 

Study of our neighboring planets not only helps us to generalize the study of 
our own, but it has the most practical hints and cautionary tales for us to read - if 
only we are wise enough to understand them. 


Tim* la K. 

Schematic temperature evolutionary tracks of the planet Earth through geological time. 
The temperature changes shown are driven by changes in the Sun's luminosity and the 
composition of the Earth's atmosphere. One aeon is a billion years. From calculations 
by the author. Courtesy, American Association for the Advancement of Science. 


21. Beginnings and Ends of the Earth 

Stars, like people, do not live forever. But the lifetime of a person is measured in 
decades, the lifetime of a star in billions of years. 

A star is born out of interstellar clouds of gas and dust. For a while, it stably 
converts hydrogen to helium in the thermonuclear furnaces of its deep interior. 
Then, in stellar old age, it encounters a set of minor or major catastrophes - a slow 
trickle or an explosive injection of star-stuff into space. During the more or less 
stable portion of the lifetime of the star, the hot interior region, converting 
hydrogen into helium, gradually eats its way outward from the very center. In the 
course of time, the star becomes slowly, almost imperceptibly, brighter. 

After the flares and other impetuosities of its early adolescence, our Sun settled 
down to a more or less constant radiation output. But four billion years ago it was 
about 30 percent dimmer than it is today. If we assume that four billion years ago 
the Earth had the same distribution of land and water, clouds and polar ice, so that 
it absorbed the same relative amount of sunlight as it does today, and if we also 
assume that it had the same atmosphere as it does today, we can calculate what its 
temperature would have been. The calculation reveals a temperature for the entire 
Earth significantly below the freezing point of seawater. In fact, even two billion 
years ago, under these assumptions, the Sun would not have been bright enough to 
keep the Earth above the freezing point. 

But we have a wide variety of evidence that this was not the case. There are in 
old mud deposits ripple marks caused by liquid water. There are pillow lavas 
produced by undersea volcanoes. There are enormous sedimentary deposits that 
can only be produced on ocean margins. There are biological products, called algal 
stromatolites, which can only be produced in water. 

So what is wrong? Either our theory of the evolution of the Sun is wrong or 
our assumption that the early Earth is like the present Earth is wrong. The theory 
of solar evolution seems to be in good shape. What uncertainties exist do not 
appear to affect the question of the Sun's early luminosity. 

The most likely resolution of this apparent paradox is that something was 
different on the early Earth. After studying a wide range of possibilities, I conclude 
that what was different, two billion years ago and earlier, was the presence of 
small quantities of ammonia in the Earth's atmosphere. Ammonia is present on 
Jupiter today; it is the form of nitrogen expected under primitive conditions. It 
absorbs very strongly at the infrared wavelengths that the Earth likes to emit to 
space. Ammonia on the primitive Earth would have held heat in, increasing the 
surface temperature through the greenhouse effect and keeping the global 
temperature of Earth at congenial levels - for the origin and early history of life 
and for liquid water to have been abundant early in the history of the planet. And 
ammonia is one of the atmospheric constituents needed for making the building 
blocks of life. The study of the Sun's evolution leads us to information about the 
early history, chemical composition, and temperature of the Earth, and, therefore, 


to the circumstances of its habitability. Stellar and biological evolution are 

What about the future evolution of the Sun? The Sun is steadily growing 
brighter. About four billion years from now the Sun will be sufficiently brighter 
that there will be a greatly enhanced runaway greenhouse effect on Earth, just as 
there is today on Venus. Our oceans will boil, and carbon dioxide, now present as 
carbonates in the sedimentary rocks, will pour out into the atmosphere. The Earth 
will be an uninhabitable cauldron. 

It is conceivable that the technology of those remote times will be equal to the 
task of preventing such a runaway, but it will be an extremely difficult engineering 
job. However, remarkably, the same increase in the brightness of the Sun some 
billions of years from now will convert Mars from a place where the average 
temperature is 100 degrees F below zero to a place that has temperatures almost 
exactly the same as those on Earth today. 

When the Earth becomes uninhabitable, Mars will gain a balmy and clement 
climate. Our remote descendants, if any, may wish to take advantage of this 


Mariner 9 composite photograph of Mars. Great volcanoes 
are seen at the bottom, the northern polar cap at tfie top. 
The amount of carbon dioxide and water frost locked in 
the polar cap, if released into the atmosphere, would probably 
produce much more Earth-like climatic conditions. Courtesy, 


22 . Terraforming the Planets 

Both subtly and profoundly, the activities of life have affected the environment of 
our planet. Our atmosphere is composed of 20 percent oxygen and 80 percent 
nitrogen. The oxygen is produced almost entirely by green-plant photosynthesis. 
Similarly, the most recent evidence suggests that nitrogen is almost entirely a 
product of the biological activity of soil micro-organisms, which convert nitrates 
and ammonia into the gas N 2 , molecular nitrogen. Not only are the principal 
constituents of our atmosphere closely controlled by biological activities, but the 
minor constituents are as well. To a significant extent, carbon dioxide is also 
buffered by the photosynthesis/ respiration feedback loop. Even so minor a 
constituent of the Earth's atmosphere as methane, CH 4 , is of biological origin. 

In fact, life on Earth, invisible to photography, could be detectable with a small 
telescope and an infrared spectrometer from the vantage point of Mars. The 
Martians, if any, could easily observe, at a wavelength of 3.33 microns in the 
infrared, a strong absorption feature that straightforward analysis would reveal to 
be due to one part per million of methane in the terrestrial atmosphere. It should 
not be difficult to deduce that the methane is probably of biological origin. 
Methane is chemically unstable in an excess of oxygen. It is oxidized rapidly to 
carbon dioxide: 

CH 4 + 20 2 =C 0 2 + 2 H 2 0 . 

The amount of methane that would be in equilibrium with the great excess of 
oxygen in our atmosphere is less than one billion billion billionth the amount 
actually observed. How can this be? Methane must be produced at a rate so rapid 
that there is not time enough for oxygen to reduce its abundance to the 
equilibrium amount. It might be that there are massive outpourings of methane 
from ancient petroleum fields on Earth. But because of the huge output required, 
this is a very unlikely hypothesis. It is far more likely that methane is produced by 
a biological process. 

And this is indeed the case. There seems to be a debate in the ecological 
literature on two possible sources of this methane. One source is methane 
bacteria, which live in swamps and marshes - hence the term "marsh gas" to refer 
to methane. The principal other habitat of methane bacteria is in the rumens of 
ungulates. There is at least one school of ecological thought that believes that 
more methane is produced from the latter source than from the former. This 
means that bovine flatulence - the intimate intestinal activities of cows, reindeer, 
elephants, and elk - is detectable over interplanetary distances, while the bulk of 
the activities of mankind are invisible. We would not ordinarily consider the 
flatulence of cattle as a dominant manifestation of life on Earth, but there it is. 

Inadvertently, with no conscious effort by mankind, life on Earth has reworked 
the environment in a major way. Through the effect of atmospheric pressure and 
composition on the climate, there is a feedback loop in which the climate itself 
may to some degree be controlled by the gas exchange reactions in which the life 


forms on Earth engage. In a way, life on Earth has terraformed Terra. It has to 
some extent made the Earth the way it is. 

Is it possible that at some time in the future we might be able similarly to 
terraform other planets, to convert a Mars or Venus, today inhospitable to Man, 
into a clement and habitable environment? Such a change, if possible at all, should 
be done only after the most careful and responsible examination of the 
consequences. We would first want to understand thoroughly the present 
environment of the planet before altering it. We must scrupulously guarantee that 
any indigenous organisms on the planet would not be disrupted by terraforming. If 
Mars, for example, has a population of indigenous organisms that would be 
extinguished by terraforming, we should never perform such terraforming. But if 
the planet is lifeless, or if the organisms survive better under conditions closer to 
our own, it might be reasonable at some time in the future to consider such an 
alteration of a planetary environment. 

Our motivations for planetary re-engineering must be clear. This is not a 
solution to the overpopulation problem. Several hundred thousand people are 
born every day on Earth. There is certainly no prospect in the immediate future of 
transshipping hundreds of thousands of people to other planets each day. In its 
entire history mankind has managed to launch one dozen people to another 
celestial body. Nor are we likely to see in the immediate future a thriving mining 
industry in which ores are extracted from another planet and transshipped to 
Earth: The freightage would be prohibitive. 

And yet the human spirit is expansive; the urge to colonize new environments 
lies deep within many of us. Such activities can be performed without cosmic 
imperialism, without the kind of arrogance that characterized the European 
colonization of the New World, or the encroachment on the Indians in the settling 
by whites of the American West. Interplanetary colonization can be consistent 
with the highest aspirations and goals of mankind. 

How would we do it? In the case of Venus, as we saw in Chapter 12, there is a 
crushing atmosphere, composed largely of carbon dioxide, and a searing surface 
temperature in excess of 900 degrees F. It would seem to be a formidable task 
indeed to convert this environment into one in which men could live and work 
without enormous technological assistance. But there is a bare possibility of re- 
engineering V enus into a quite Earth-like place, a possibility I suggested with some 
caution in 1961. The method assumes that the high surface temperature is 
produced by a greenhouse effect involving carbon dioxide and water, a conjecture 
that is much more plausible now than it was then. The idea is simply to seed the 
clouds of Venus with a hardy variety of algae - a genus called Nostocacae was 
suggested - which would perform photosynthesis in the vicinity of the clouds. 
Carbon dioxide and water would be converted into organic compounds, largely 
carbohydrates, and oxygen. The algae would, however, be carried by the 
atmospheric circulation down to deeper and hotter levels in the Venus 
atmosphere, where they would be fried. Frying an alga releases simple carbon 


compounds, carbon, and water into the atmosphere. The water content of the 
atmosphere thus remains fixed, and the net result is the conversion of carbon 
dioxide into carbon and oxygen. 

The present greenhouse effect on Venus is due largely to carbon dioxide and 
water. The present total pressure on Venus is about ninety times that on the 
surface of Earth. The Venus atmosphere is largely composed of carbon dioxide. As 
the carbon dioxide is converted into carbon and oxygen, and the oxygen is 
chemically combined with the crust of Venus, the total pressure would decline, 
decreasing atmospheric infrared absorption, reducing the greenhouse effect, and 
lowering the temperature. 

It is possible, therefore, that the injection of appropriately grown algae into the 
clouds of V enus, algae able to reproduce there faster than they are fried, would in 
time convert the present extremely hostile environment of V enus into one much 
more pleasant for human beings. 

The amount of water vapor in the Venus atmosphere, if condensed on the 
surface of the planet, would give a layer of water about one foot high - not an 
ocean, but enough to do irrigation and to provide for other human needs. It is also 
possible that water is available bound to the rocks on the surface of the planet. 

No one can estimate whether this is a very likely scenario, or how long it 
would take to re-engineer the second planet from the Sun. It is perfectly possible 
that there is some flaw in the idea. For example, the high surface temperature may 
not be due to a greenhouse effect, but I think this is unlikely. 

In any case, I think terraforming Venus is not impossible. The Nostoc scheme 
is an example of how human technology and science may, in periods quite short 
compared to geological time, rework the environment of another planet. 

For Mars, as we saw in Chapter 18, there is now evidence that in comparatively 
recent times conditions on that planet were much more Earth-like than they are 
today. We mentioned the likelihood that enormous quantities of carbon dioxide 
and water are locked in the Martian polar caps, trapped as permafrost and 
chemically bound to the surface material elsewhere on the planet. Much of this 
CO, and H 2 0 may be released from the polar caps into the atmosphere twice each 
precessional cycle of fifty thousand years. Drs. Joseph Burns and Martin Harwit of 
Cornell University have considered a variety of technological schemes to induce 
more clement conditions on Mars hundreds of years from now, rather than 
thousands. These schemes involve alteration of the orbits of the Martian satellites 
or of a nearby asteroid to change the precessional motion of the planet, or the 
installation of an enormous orbiting mirror over the polar cap to melt the material 
frozen there. Even easier, however, might be to sprinkle carbon black over the 
caps, heat up the poles, increase the atmospheric pressure, and warm the planet. 

Again, we do not know that such schemes will work, but they do not seem 
extremely impractical. It may very well be that on time scales of hundreds of years 
we will have the capability of converting Mars into a much more Earth-like planet 
than it would otherwise be. 


The Moon and the asteroids are much less hospitable than Mars and Venus. 
They are so much less able to retain an atmosphere that the terraforming schemes 
we have been discussing are inapplicable to them. But even on airless worlds, the 
establishment of human colonies on their surfaces or even - in the case of small 
asteroids - in their interiors seems a possible future project for mankind. Such 
colonies would be much more constrained than those on a re-engineered Mars or 
Venus, and would require much greater attention to the husbanding of scarce 

Such colonies would be tenable only if significant natural resources - 
particularly frozen or chemically bound water - were to be found. In the case of 
the very surface of the Moon, the samples returned by Apollo astronauts showed 
virtually no such water at all. But it is entirely possible that large stores of water 
exist in cold, shadowed regions near the lunar poles or at substantial depths 
beneath the lunar surface. 

It is not unlikely that on a time scale of a few centuries there will be extensive 
human colonies throughout the inner part of the Solar System and on some of the 
major satellites of the Jovian planets. The prospect is, of course, a difficult one; the 
engineering tasks are immense and the need to retain ecological respect for other 
environments pervasive. The danger of both forward and backward biological 
contamination must always be examined scrupulously. 

There may even come a day when we shall be called to account for our 
stewardship of the Solar System. From that vantage point our own epoch will be 
viewed as a moment when we first left the cradle of our species and began, in a 
groping and tentative way, to explore and transform the space surrounding us. 


A jpace caravel. Picture by Jon Loinberg after a drawing by 


23. The Exploration and Utilization of the Solar 


At the very beginning of the twentieth century competent scientific and lay 
opinion held that airplanes were impossible. The end of the century, barring the 
dark specter of nuclear or ecological catastrophes, will probably see joint Soviet 
and American manned space expeditions to the nearer planets. 

This is the century in which some of the oldest dreams of Man have been 
realized, in which mankind has sprouted wings and realized the aspirations of 
Daedalus and da Vinci. Air-breathing, man-carrying machines now circumnavigate 
our planet in less than a day; other machines, skimming above the atmosphere, 
carry men around our globe in ninety minutes. 

There is a generation of men and women for whom, in their youth, the planets 
were unimaginably distant points of light, and the Moon was the paradigm of the 
unattainable. Those same men and women, in middle life, have seen their fellows 
walk upon the surface of the Moon; in their old age, they will likely see men 
wandering along the dusty surface of Mars, their journeys illuminated by the 
battered face of Phobos. There is only one generation of humans in the ten- 
million-year history of mankind that will live through such a transition. That 
generation is alive today. 

This is also the moment in our history when, for the first time, the whole of 
our planet has been explored, when tribalism is dissipating, when great 
transnational groupings of states are being organized, when stunning technological 
advances in communications and transportation are eroding the cultural 
differences among the various segments of mankind. 

But cultural diversity is the forge for the survival of our civilization, just as 
biological diversity is the forge for the survival of life. 

The Earth is overcrowded. Not yet in a literal sense: Our technology is 
adequate to maintain comfortably a population significantly larger than our 
present 3.6 billion. The Earth is overcrowded in a psychological sense. For that 
restless and ambition-driven fraction of mankind that has blazed new paths for our 
species, there are no new places to go. There are places inside of ourselves, but this 
is not the forte of such individuals. There are the ocean basins, but we are not yet 
committed to exploring them seriously; and when we do, they are likely to be 
exploited rapidly. 

At just this time in our history comes the possibility of exploring and 
colonizing our neighboring worlds in space. The opportunity has come to us not a 
moment too soon. 

October 12, 1992, will be the five hundredth anniversary of the discovery of the 
"New World" by Christopher Columbus. Mankind will be, I think, engaged at that 
very moment in an enterprise similar to Columbus'. We will have advantages over 
him and the mariners of his time. We know precisely where we are going and how 


to get there. The way will have been examined by unmanned vessels going before 
us. The paths will have been charted exactly. There will be hazards - collisions 
with asteroids on voyages to the outer Solar System, for example, or mechanical 
failure. But there will be no fear of slipping off the edge of the world, as many of 
the sailors of Columbus' time truly feared. And very likely there will not be a 
Solar System equivalent of doldrums or sea monsters. Yet the same thrill of 
exploration and the same adventuresome spirit that drove Columbus will be 
driving us. As the discovery and exploration of the New World had a profound 
and irreversible effect on European civilization, exploration and colonization of 
the Solar System will produce permanent changes in the history and development 
of mankind. 

The analogy with the epic sea voyages of centuries ago is, it seems to me, 
remarkably close. There was the initial set of sea voyages by Columbus, an Italian 
in the Spanish court. Our initial set of manned Apollo explorations of the Moon 
was motivated in significant part by a group of expatriate German engineers led 
by Wernher von Braun. After Columbus' four voyages, there was essentially a 
hiatus of a decade or so - and then a burst of further exploratory activities by the 
Spanish, English, French, and Dutch — vessels flying many flags, many expeditions 
organized by foreign nationals. 

Apollo iy marked the end of the Apollo lunar missions. It seems clear, at least 
in the United States, that there will be a hiatus of a decade or more before further 
lunar exploration and lunar bases are organized. Apollo's primary orientation was 
never scientific. It was conceived at a time of political embarrassment for the 
United States. Several historians have suggested that a principal motivation of 
President Kennedy in organizing the Apollo program was to deflect public 
attention from the stinging defeat suffered at the Bay of Pigs invasion. Several tens 
of billions of dollars have been expended on the Apollo program. If the objective 
had been scientific exploration of the Moon, it could have been carried out much 
more effectively, for much less money, by unmanned vehicles. The early Apollo 
missions went to lunar sites of little scientific interest, because the safety of the 
astronauts was the prime, almost the only, concern. Only toward the very end of 
the Apollo series did scientific considerations play a significant role. 

The Apollo program ended just as the first scientist landed on the Moon. 
Harrison "Jack" Schmitt, a geologist, trained at Harvard, was one of the two-man 
crew of the Apollo iy landing module. He was the first scientist to study the Moon 
from the surface of the Moon. It is ironic that just as the Apollo program became 
able to achieve this major advance in the scientific exploration of the Moon, it was 
canceled. Fittingly enough, the first scientist to land on the Moon was the last man 
to land on the Moon - at least in the foreseeable future. There are no plans for 
follow-on manned missions to the Moon either by the United States or, so far as 
we know, by the Soviet Union. 

The argument for cancellation of Apollo was economic. Yet the incremental 
cost of a given mission was in the many tens of millions of dollars, something like 


one thousandth the total cost of the Apollo program. It is very much as if, against 
the advice of my wife, I purchase a Rolls-Royce automobile. She argues that a 
Volkswagen could get me round just as well, but I feel that a Rolls-Royce would 
take my mind off the troubles of my job. I then spend so much money on the 
Rolls-Royce that, after driving it a little bit, I find I can drive it no more because I 
cannot afford the price of a tank of gas - which is about one thousandth the cost 
of a Rolls-Royce. 

I was one of the scientists opposed to an early Apollo mission. But once the 
Apollo technology was in hand, I was very much for its continuing usage. I believe 
the wrong decision was made twice - once in opting for early manned missions to 
the Moon, and later in abandoning such missions. After Apollo iy, the United 
States is left with no program, manned or unmanned, for exploration of the Moon. 
The Soviet Union has developed, in its Luna series of unmanned spacecraft, a 
proven and versatile capability for roving exploration of the lunar surface and 
automatic sample return to Earth. 

The example of the earliest exploration of the New World suggests that the 
hiatus in space will be only temporary. The linkage of Soyuz and Skylab, the 
orbital stations of the Soviet Union and the United States, scheduled for 1975 or 
1976, is presaged as the predecessor for joint manned planetary missions. 

The Solar System is much vaster than the Earth, but the speeds of our 
spacecraft are, of course, much greater than the speeds of the sailing ships of the 
fifteenth and sixteenth centuries. The spacecraft trip from the Earth to the Moon 
is faster than was the galleon trip from Spain to the Canary Islands. The voyage 
from Earth to Mars will take as long as did the sailing time from England to North 
America; the journey from Earth to the moons of Jupiter will require about the 
same time as did the voyage from France to Siam in the eighteenth century. 
Moreover, the fraction of the gross national product of the United States or the 
Soviet Union that is being expended even in the more costly manned space 
programs is just comparable to the fraction of the gross national product spent by 
England and France in the sixteenth and seventeenth centuries on their 
exploratory ventures by sailing ships. In economic terms and in human terms, we 
have performed such voyages before! 

I believe we will see semipermanent bases on the Moon by the 1980s. They 
will initially be resupplied with material and personnel from Earth, but will 
become increasingly self-sustaining, utilizing lunar resources. There will be 
children born in such colonies. They will eventually think of the Earth as "the old 
country" - an old-fashioned world in many senses, set in its ways, not moving with 
the times, more constrained and less free than the lunar colonies, despite the rigors 
and technological constraints of life on the Moon. 

In the comparatively near future the entire Solar System will be explored by 
sophisticated unmanned space vehicles. I think we will see by the 1980s and 1990s 
deep-entry probes into the atmospheres of Jupiter and Saturn and Titan (the 
biggest moon of Saturn) - places that are, I believe, far and away the most 


favorable in the Solar System for indigenous life; we will witness passages of small 
spacecraft through comets, landings on the large satellites of Jupiter and Saturn, 
flybys as far as Neptune and Pluto, and hardy spacecraft that plunge into the Sun, 
radioing back data before they sear and melt in the interior inferno of the nearest 

Human landings on even the nearer planets, however, will not be as easy as had 
once been thought. The surface of Venus, far from being Eden, turns out, as we 
have seen, to be far more like Hell. We cannot imagine manned exploration of the 
V enus surface in the next few decades. V enus is a planet with fiery temperatures, 
noxious gases, and crushing atmospheric pressures. Y et, the clouds of V enus are in 
a clement environment; and a manned buoyant probe - something like a 
nineteenth- century balloon gondola in which the astronauts work in shirtsleeves 
and leather oxygen masks - is not without its charm or its scientific interest. 

Mars is a vastly exciting planet, of enormous geological, meteorological, and 
biological interest. A manned expedition to Mars would be very desirable, except 
for two objections. First, the cost would be crushing. One hundred billion to two 
hundred billion dollars is probably a conservative estimate. I cannot bring myself 
to believe that such an expenditure is necessary in the next few decades - when 
there is so much misery on Earth that could be relieved by such expenditures. Y et 
in the longer term, say, in the first decades of the twenty-first century, I do not 
think that such cost objections will be cogent - particularly because new 
propulsion and life-support systems will be developed. 

The second objection to manned missions to Mars is more subtle. It is equally 
an objection to automatically returned samples from Mars, like the Soviet Union's 
Luna series for automatic sample return from the Moon. This is the danger of 
"back contamination." Precisely because Mars is an environment of great potential 
biological interest, it is possible that on Mars there are pathogens, organisms 
which, if transported to the terrestrial environment, might do enormous biological 
damage — a Martian plague, the twist in the plot of H. G. Wells' War of the 
Worlds, but in reverse. This is an extremely grave point. On the one hand, we can 
argue that Martian organisms cannot cause any serious problems to terrestrial 
organisms, because there has been no biological contact for 4.5 billion years 
between Martian and terrestrial organisms. On the other hand, we can argue 
equally well that terrestrial organisms have evolved no defenses against potential 
Martian pathogens, precisely because there has been no such contact for 4.5 billion 
years. The chance of such an infection may be very small, but the hazards, if it 
occurs, are certainly very high. Wholesale exterminations of native populations in 
Santo Domingo and Samoa and Tahiti occurred during the early days of sailing- 
ship exploration for just such reasons. Among the gifts carried by Columbus to the 
New World was smallpox. 

It is no use arguing that samples can be brought back safely to Earth, or to a 
base on the Moon, and thereby not be exposed to Earth. The lunar base will be 
shuttling passengers back and forth to Earth; so will a large Earth orbital station. 


The one clear lesson that emerged from our experience in attempting to isolate 
Apollo-returned lunar samples is that mission controllers are unwilling to risk the 
certain discomfort of an astronaut - never mind his death - against the remote 
possibility of a global pandemic. When Apollo u, the first successful manned lunar- 
lander, returned to Earth - it was a spaceworthy, but not a very seaworthy, vessel 
- the agreed-upon quarantine protocol was immediately breached. It was adjudged 
better to open the Apollo n hatch to the air of the Pacific Ocean and, for all we 
then knew, expose the Earth to lunar pathogens, than to risk three seasick 
astronauts. So little concern was paid to quarantine that the aircraft-carrier crane 
scheduled to lift the command module unopened out of the Pacific was 
discovered at the last moment to be unsafe. Exit from Apollo n was required in the 
open sea. 

There is also the vexing question of the latency period. If we expose terrestrial 
organisms to Martian pathogens, how long must we wait before we can be 
convinced that the pathogen-host relationship is understood? For example, the 
latency period for leprosy is more than a decade. Because of the danger of back- 
contamination of Earth, I firmly believe that manned landings on Mars should be 
postponed until the beginning of the next century, after a vigorous program of 
unmanned Martian exobiology and terrestrial epidemiology. 

I reach this conclusion reluctantly. I, myself, would love to be involved in the 
first manned expedition to Mars. But an exhaustive program of unmanned 
biological exploration of Mars is necessary first. The likelihood that such 
pathogens exist is probably small, but we cannot take even a small risk with a 
billion lives. Nevertheless, I believe that people will be treading the Martian 
surface near the beginning of the twenty-first century. 

Beyond that, it is just possible to glimpse the outline of further exploration and 
colonization. The large moons of Jupiter, and Titan, the biggest moon of Saturn, 
are major worlds in their own right. Titan is known to have an atmosphere much 
thicker than that of Mars. These five moons all have large quantities of ices on 
their surfaces. To make these worlds more habitable, their ices can be tapped for 
fuel, for the production of food and for the generation of atmospheres. Schemes 
for similarly terraforming Mars and V enus have been suggested and will very likely 
be refined and implemented (see Chapter 22). More exotic possibilities, requiring 
much more advanced technologies, are not at all beyond the likely capabilities of 
mankind in the next century or two. These include the establishment of bases on 
and in the asteroids and the short-period comets. 

In another century or so, novel forms of propulsion within the Solar System 
will be developed. One of the most charming of these is solar sailing, the use of 
the pressure of sunlight and of the protons and electrons in the solar wind for 
tripping through the Solar System. Enormous sails will be required for such an 
enterprise, but they can be extremely thin. We can imagine a spacecraft 
surrounded with tens of miles of golden gossamer-thin sails, delicately and 
exquisitely furled to catch the solar wind. Remote scientific stations will be on the 


lookout for the gusts produced by solar flares. Going outward from the Sun will 
be easy; tacking inward will be more difficult. Spacecraft using solar electric power 
and nuclear fusion will very likely also be developed in the next century. 

In something like two or three centuries, assuming even a modest growth in 
our technological capability, I would imagine the entire Solar System will have 
been explored thoroughly - at least to the extent that the Earth has been explored 
at the present time, some two or three centuries after the first large-scale 
exploration and colonization activities were begun by European sailing vessels. 
After that, it is not out of the question that a more wholesale rearrangement of 
our Solar System will begin, first slowly and then at a more rapid rate - 
astroengineering projects to move the planets about, to rearrange their masses for 
the convenience of mankind, his descendants, and his inventions. 

By then - perhaps long before then - we may have made contact with other 
advanced civilizations in the Galaxy. Or perhaps not. In any case, we will be ready 
in a few centuries for the next step. At just the point the Solar System begins to 
be filled in - again psychologically, rather than physically - we will be ready for 
interstellar voyages. That is a limitless prospect, one that can occupy the best 
exploratory instincts of mankind forever. 

Pioneer io is the first interstellar spacecraft launched by mankind. It was also 
the fastest spacecraft launched, to the date of its departure. But it will take eighty 
thousand years for Pioneer io to reach the distance of the nearest star. Because 
space is so empty, it will never enter another Solar System. The little golden 
message aboard Pioneer io will be read, but only if there are interstellar voyagers 
able to detect and intercept Pioneer io. 

I believe that such an interception may occur, but by interstellar voyagers from 
the planet Earth, overtaking and heaving to this ancient space derelict - as if the 
Nina, with its crew jabbering in Castilian about falling off the edge of the world, 
were to be intercepted, somewhere off Tristan da Cunha, by the aircraft carrier 
John F. Kennedy. 

Human figure and star field. A drawing by Robert MacIntyre. 

Part Three: 


To dance beneath the diamond sky 
With one hand wavin' free . . . 

- Bob Dylan, Mr. Tambourine Man 


Three dolphins, conversing with the author. Photograph by 
the author. 


24. Some of My Best Friends Are Dolphins 

The first scientific conference on the subject of communication with 
extraterrestrial intelligence was a small affair sponsored by the U. S. National 
Academy of Sciences in Green Bank, West Virginia. It was held in 1961, a year 
after Project Ozma, the first (unsuccessful) attempt to listen to possible radio 
signals from civilizations on planets of other stars. Subsequently, there were two 
such meetings held in the Soviet Union sponsored by the Soviet Academy of 
Sciences. Then, in September 1971, a joint Soviet-American conference on 
Communication with Extraterrestrial Intelligence was held near Byurakan, in 
Soviet Armenia (see Chapter 27). The possibility of communication with 
extraterrestrial intelligence is now at least semirespectable, but in 1961 it took a 
great deal of courage to organize such a meeting. Considerable credit should go to 
Dr. Otto Struve, then director of the National Radio Astronomy Observatory, 
who organized and hosted the Green Bank meeting. 

Among the invitees to the meeting was Dr. John Lilly, then of the 
Communication Research Institute, in Coral Gables, Florida. Lilly was there 
because of his work on dolphin intelligence and, in particular, his efforts to 
communicate with dolphins. There was a feeling that this effort to communicate 
with dolphins - the dolphin is probably another intelligent species on our own 
planet - was in some sense comparable to the task that will face us in 
communicating with an intelligent species on another planet, should interstellar 
radio communication be established. I think it will be much easier to understand 
interstellar messages, if we ever pick them up, than dolphin messages (see Chapter 
29), if there are any. 

The conjectured connection between dolphins and space was dramatized for 
me much later, at the lagoon outside the Vertical Assembly Building at Cape 
Kennedy, as I awaited the Apollo 17 liftoff. A dolphin quietly swam about, 
breaking water now and again, surveying the illuminated Saturn booster poised for 
its journey into space. Just checking us all out, perhaps? 

Many of the participants at the Green Bank meeting already knew one another. 
But Lilly was, for many of us, a new quantity. His dolphins were fascinating, and 
the prospect of possible communication with them was enchanting. (The meeting 
was made further memorable by the announcement in Stockholm during its 
progress that one of our participants, Melvin Calvin, had been awarded the Nobel 
Prize in Chemistry. ) 

For many reasons, we wished to commemorate the meeting and maintain some 
loose coherence as a group. Captured as we were by Lilly's tales of the dolphins, 
we christened ourselves "The Order of the Dolphins." Calvin had a tie pin struck 
as an emblem of membership; it was a reproduction from the Boston Museum of 
an old Greek coin showing a boy on a dolphin. I served as a kind of informal 
coordinator of correspondence the few times that there was any "Dolphin" 
business, all of it the election of new members. In the following year or two, we 


elected a few others to membership - among them I. S. Shklovskii, Freeman 
Dyson, and J. B. S. Haldane. Haldane wrote me that membership in an 
organization that had no dues, no meetings, and no responsibilities was the sort of 
organization he appreciated; he promised to try hard to live up to the duties of 

The Order of the Dolphins is now moribund. It has been replaced by a number 
of activities on an international scale. But for me the Order of the Dolphins had a 
special significance - it provided an opportunity to meet with, talk with, and, to 
some extent, befriend dolphins. 

It was my practice to spend a week or two each winter in the Caribbean, 
mostly snorkeling and scuba diving - examining the non-mammalian inhabitants 
of the Caribbean waters. Because of my acquaintance and later friendship with 
John Lilly, I was also able to spend some days with Lilly's dolphins in Coral Gables 
and in his research station at St. Thomas in the U. S. V irgin Islands. 

His institute, now defunct, unquestionably did some good work on the 
dolphin, including the production of an important atlas of the dolphin brain. 
While I will be critical here about some of the scientific aspects of Lilly's work, I 
want to express my admiration for any serious attempt to investigate dolphins and 
for Lilly's pioneering efforts in particular. Lilly has since moved on to 
investigations of the human mind from the inside - consciousness expansion, both 
pharmacologically and non-pharmacologically induced. 

I first met Elvar in the winter of 1963. Laboratory research on dolphins had 
been limited by these mammals' sensitive skin; it was only the development of 
plastic polymer tanks that permitted long-term residence of dolphins in the 
laboratory. I was surprised to find that the Communication Research Institute 
resided in what used to be a bank, and I had visions of a polystyrene tank in each 
teller's cage, with dolphins counting the money. Before introducing me to Elvar, 
Lilly insisted that I don a plastic raincoat, despite my assurances that this was 
entirely unnecessary. We entered a medium-sized room at the far corner of which 
was a large polyethylene tank. I could immediately see Elvar with his head thrown 
back out of the water so that the visual fields of each eye overlapped, giving him 
binocular vision. He swam slowly to the near side of the tank. John, the perfect 
host, said, "Carl, this is Elvar; Elvar, this is Carl." Elvar promptly slapped his head 
forward, down onto the water, producing a needle-beam spray of water that hit 
me directly on the forehead. I had needed a raincoat after all. John said, "Well, I 
see you two are getting to know each other" - and promptly left. 

I was ignorant of the amenities in dolphin/human social interactions. I 
approached the tank as casually as I could manage and murmured something like 
"Hi, Elvar." Elvar promptly turned on his back, exposing his abraded, gun-metal- 
gray belly. It was so much like a dog wanting to be scratched that, rather gingerly, I 
massaged his underside. He liked it - or at least I thought he liked it. Bottle-nose 
dolphins have a sort of permanent smile set into their heads. 


After a little while, Elvar swam to the opposite side of the tank and then 
returned, again presenting himself supine - but this time about six inches 
subsurface. He obviously wanted his belly scratched some more. This was slightly 
awkward for me because I was outfitted under my raincoat with a full armory of 
shirt, tie, and jacket. Not wishing to be impolite, I took off my raincoat, removed 
my jacket, slid my sleeves up onto my wrists without unbuttoning my shirt cuffs, 
and put my raincoat on again, all the while assuring Elvar I would return 
momentarily — which I did, finally scratching him six inches below the water. 
Again he seemed to like it; again, after a few moments, he retreated to the far side 
of the tank, and then returned. This time he was about a foot subsurface. 

My mood of cordiality was eroding rapidly, but it seemed to me that Elvar and 
I were at least engaged in communication of a kind. So I once again removed my 
raincoat, rolled up my sleeves, put my raincoat on again, and attended to Elvar. 
The next sequence found Elvar three or four feet subsurface, awaiting my massage. 
I could just have reached him were I prepared to discard raincoat and shirt 
altogether. This, I decided, was going too far. So we gazed at each other for a while 
in something of a standoff - man and dolphin, with a meter of water between us. 
Suddenly, Elvar came booming out of the water head first, until only his tail flukes 
were in contact with the water. He towered over me, doing a kind of slow back- 
pedaling, then uttered a noise. It was a single "syllable," high-pitched and squeaky. 
It had, well, a sort of Donald Duck timbre. It sounded to me that Elvar had said 

I bounded out of the room, found John attending to some electronic 
equipment, and announced excitedly that Elvar had apparently just said "Morel" 

John was laconic. "Was it in context?" was all he asked. 

"Yes, it was in context." 

"Good, that's one of the words he knows." 

Eventually, John believed that Elvar had learned some dozens of words of 
English. To the best of my knowledge, no human has ever learned a single word of 
delphinese. Perhaps this calibrates the relative intelligence of the two species. 

Since the time of Pliny, human history has been full of tales of a strange 
kindred relation between humans and dolphins. There are innumerable 
authenticated accounts of dolphins saving human beings who would otherwise 
have drowned, and of dolphins protecting human beings from attack by other sea 
predators. As recently as September 1972, according to an account in the New 
York Times, two dolphins protected a twenty-three-year-old shipwrecked woman 
from predatory sharks during a twenty-five-mile swim in the Indian Ocean. 
Dolphins are pervasive and dominant motifs in the art of some of the most ancient 
Mediterranean civilizations, including the Nabatean and Minoan. The Greek coin 
that Melvin Calvin had duplicated for us is an expression of this long-standing 

What humans like about dolphins is clear. They are friendly, and faithful; at 
times they provide us with food (some dolphins have herded sea animals to 


fishermen); and they occasionally save our lives. Why dolphins should be attracted 
to human beings, what we do for them, is far less clear. I will propose later in this 
chapter that what we provide for dolphins is intellectual stimulation and audio 

John was replete with dolphin anecdotes of first- or secondhand. I remember 
three stories in particular. In one, a dolphin was captured in the open sea, put 
aboard a small ship in a plastic tank, and confronted his captors with a set of 
sounds, whistles, screeches, and drones that had a remarkably imitative character. 
They sounded like seagulls, fog horns, train whistles - the noises of shore. The 
dolphin had been captured by shore creatures and was attempting to make shore 
talk, as a well-brought-up guest would. 

Dolphins produce most of their sounds with their blow hole, which produces 
the spout of water in their cousins the whales, of whom they are close, miniature 
anatomical copies. 

In another tale, a dolphin held in captivity for some time was let loose in the 
open sea and followed. When it made contact with a school of dolphins, there was 
an extremely long and involved sequence of sounds from the liberated prisoner. 
Was it an account of his imprisonment? 

Besides their echo-location clicks - a very effective underwater sonar system - 
dolphins have a kind of whistle, a kind of squeaky-door noise, and the noise made 
when imitating human speech, as in Elvar's "Morel" They are capable of producing 
quite pure tones, and pairs of dolphins have been known to produce tones of the 
same frequency and different phase, so that the "beat" phenomenon of wave 
physics occurs. The beat phenomenon is a lot of fun. If humans could sing pure 
tones, I am sure we would go on beating for hours. 

There is little doubt that the whistle noises are used for dolphin 
communications. I heard what seemed to be (I may be anthropomorphizing) very 
plaintive whistles on St. Thomas from a male adolescent dolphin named Peter, 
who, for a while, was kept in isolation from two adolescent female dolphins. They 
all whistled a lot at each other. When the three were reunited in the same pool, 
their sexual activity was prodigious, and they did not whistle much. 

Most of the communication among dolphins that I have heard is of the 
squeaky-door variety. Dolphins seem to be attracted to humans who make similar 
noises. In March 1971, for example, in a dolphin pool in ffawaii, I spent forty-five 
minutes of vigorous squeaky-door "conversation" with several dolphins, to at least 
some of whom I seemed to be saying something of interest. In delphinese it may 
have been stupefying in its idiocy, but it held their attention. 

In another story, John told how it was his practice with dolphins of adolescent 
age and sexual proclivities to separate male and female over the weekend when 
there would be no experiments. Otherwise, they would do what John, with some 
delicacy, described as "going on a honeymoon" - which, however desirable to the 
dolphins, would leave them in no condition for experimentation on Monday 
morning. In one case, dolphins could pass across a large tank, from one half to the 


other, only through a heavy, vertically sliding door. One Monday morning John 
found the door in place but the two dolphins of opposite sex, Elvar and Chi-Chi, 
on the same side of the barrier. They had gone on a honeymoon. John's 
experimental protocol would have to wait, and he was angry. Who had forgotten 
to separate the dolphins on Friday afternoon? But everyone remembered that the 
dolphins had been separated and the door properly closed. 

As a test, the experimenters repeated the conditions. Elvar and Chi-Chi were 
separated and the heavy door put in place amid Friday-afternoon ceremonies of 
loud goodbyes, slammings of building doors, and the heavy trodding of exiting feet. 
But the dolphins were being observed covertly. When all was quiet, they met at 
the barrier and exchanged a few low-frequency creaking-door noises. Elvar then 
pushed the door upward at one corner from his side until it wedged; Chi-Chi, 
from her side, pushed the opposite corner. Slowly, they worked the door up. Elvar 
came swimming through and was received by the embraces ("enfinments" is not 
the right word, either) of his mate. Then, according to John's story, those who lay 
in waiting announced their presence by whistling, hooting, and booing — 
whereupon, with some appearance of embarrassment, Elvar swam to his half of 
the pool and the two dolphins worked down the vertical door from their opposite 

This story has such an appealing human character to it - even down to a little 
dollop of V ictorian sexual guilt — that I find it unlikely. But there are many things 
that are unlikely about dolphins. 

I am probably one of the few people who has been "propositioned" by a 
dolphin. The story requires a little background. I went to St. Thomas one winter 
to dive and to visit Lilly's dolphin station, which was then headed by Gregory 
Bateson, an Englishman of remarkable and diverse interests in anthropology, 
psychology, and human and animal behavior. Dining with some friends at a fairly 
remote mountaintop restaurant, we engaged in casual conversation with the 
hostess at the restaurant, a young woman named Margaret. She described to me 
how uneventful and uninteresting her days were (she was hostess only at night). 
Earlier the same day Bateson had described to me his difficulties in finding 
adequate research assistants for his dolphin program. It was not difficult to 
introduce Margaret and Gregory to each other. Margaret was soon working with 

After Bateson left St. Thomas, Margaret was for a while de facto director of the 
research station. In the course of her work, Margaret performed a remarkable 
experiment, described in some detail in Lilly's book The Mind of the Dolphin. She 
began living on a kind of suspended raft over the pool of Peter the dolphin, 
spending twenty-four hours a day in close contact with him. Margaret's 
experiment occurred not long before the incident I now speak of; it may have had 
something to do with Peter's attitude toward me. 

I was swimming in a large indoor pool with Peter. When I threw the pool's 
rubber ball to Peter (as was natural for me to have done), he dove under the ball 


as it hit the water and batted it with his snout accurately into my hands. After a 
few throws and precision returns, Peter's returns became increasingly inaccurate - 
forcing me to swim first to one side of the pool and then to the other in order to 
retrieve the ball. Eventually, it became clear that Peter chose not to place the ball 
within ten feet of me. He had changed the rules of the game. 

Peter was performing a psychological experiment on me - to learn to what 
extreme lengths I would go to continue this pointless game of catch. It was the 
same kind of psychological testing that Elvar had conducted in our first meeting. 
Such testing is one clue to the bond that draws dolphins to humans: We are one of 
the few species that have pretensions of psychological knowledge; therefore, we 
are one of the few that would permit, however inadvertently, dolphins to perform 
psychological experiments on us. 

As in my first interview with Elvar, I eventually saw what was happening and 
decided stoutly that no dolphin was going to perform a psychological experiment 
on me. So I held the ball and merely tread water. After a minute or so, Peter swam 
rapidly toward me and made a grazing collision. He circled around and repeated 
this strange performance. This time I felt some protrusion of Peter's lightly 
brushing my side as he passed. As he circled for a third pass, I idly wondered what 
this protrusion might be. It was not his tail flukes, it was not . . . Suddenly it 
dawned on me, and I felt like some maiden aunt to whom an improper proposal 
had just been put. I was not prepared to cooperate, and all sorts of conventional 
expressions came unbidden to my mind - like, "Don't you know any nice girl 
dolphins?" But Peter remained cheerful and unoffended by my unresponsiveness. 
(Is it possible, I now wonder, that he thought I was too dense to understand even 
that message?) 

Peter had been separated from female dolphins for some time and, in the not 
too distant past, had spent many days in close contact, including sexual contact, 
with Margaret, another human being. I do not think that there is any sexual bond 
that accounts for the closeness that dolphins feel toward humans, but the incident 
had some significance. Even in what we piously describe as "bestiality" there are 
only a few species which, so far as I have heard, are put upon by human beings for 
interspecific sexual activities; these are entirely of the sort that humans have 
domesticated. I wonder if some dolphins have thoughts about domesticating us. 

Dolphin anecdotes make marvelous cocktail party accounts, an unending 
source of casual conversation. One of the difficulties that I discovered with 
research into dolphin language and intelligence was precisely this fascination with 
anecdote; the really critical scientific tests were somehow never performed. 

For example, I repeatedly urged that the following experiment be done: 
Dolphin A is introduced into a tank that is equipped with two underwater audio 
speakers. Each hydrophone is attached to an automatic fish dispenser catering tasty 
dolphin fare. One speaker plays Bach, the other plays Beatles. 

Which speaker is playing Bach or Beatles (a different composition each time) at 
any given moment is determined randomly. Whenever Dolphin A goes to the 


appropriate speaker - let us say, the one playing Beatles - he is rewarded with a 
fish. I think there is no doubt that any dolphin will - because of his great interest 
in, and facility with, the audio spectrum - be able soon to distinguish between 
Bach and Beatles. But that is not the significant part of the experiment. What is 
significant is the number of trials before Dolphin A becomes sophisticated - that 

is, always knows that if he wishes a fish he should go to the speaker playing 

Now Dolphin A is separated from the speakers by a barrier of plastic broad- 
gauge mesh. He can see through the barrier, he can smell and taste through it, and, 
most important, he can hear and "speak" through it. But he cannot swim through 

it. Dolphin B is then introduced into the area of the speakers. Dolphin B is naive; 
that is, he has had no prior experience with underwater fish dispensers, Bach, or 
Beatles. Unlike the well-known difficulty in finding "naive" college students with 
whom to perform experiments on cannibis sativa, there should be no difficulty 
finding dolphins lacking extensive experience with Bach and Beatles. Dolphin B 
must go through the same learning procedure as did Dolphin A. But now each 
time that Dolphin B (at first randomly) succeeds, not only does the dispenser 
provide him with a fish, but a fish is also thrown to Dolphin A, who is able to 
witness the learning experience of Dolphin B. If Dolphin A is hungry, it is 
distinctly to his advantage to communicate what he knows about Bach and Beatles 
to Dolphin B. If Dolphin B is hungry, it is to his advantage to pay attention to the 
information that Dolphin A may have. The question, therefore, is: Does Dolphin B 
have a steeper learning curve than Dolphin A? Does he reach the plateau of 
sophistication in fewer trials or less time? 

If such experiments were repeated many times and it were found that the 
learning curves for Dolphin B were in a statistically significant sense always steeper 
than those of Dolphin A, communication of moderately interesting information 
between two dolphins would have been established. It might be a verbal 
description of the difference between Bach and the Beatles — to my mind, a 
difficult but not impossible task — or it might simply be the distinction between 
left and right in each trial, until Dolphin B catches on. This is not the best 
experimental design to test dolphin-to-dolphin communication, but it is typical of 
a large category of experiments that could be performed. To my knowledge and 
regret, no such experiments have been performed with dolphins to date. 

Questions of dolphin intelligence have taken on a special poignancy for me in 
the past few years as the case of the humpback whale unfolded. In a remarkable 
set of experiments, Roger Payne, of Rockefeller University, has trailed 
hydrophones to a depth of tens of meters in the Caribbean, seeking and recording 
the songs of the humpback whale. Another member, along with the dolphins, of 
the taxonomic class of Cetacea, the humpback whale has extraordinarily complex 
and beautiful articulations, which carry over considerable distances beneath the 
ocean surface, and which have an apparent social utility within and between 
schools of whales, which are very gregarious social animals. 


The brain size of whales is much larger than that of humans. Their cerebral 
cortexes are as convoluted. They are at least as social as humans. Anthropologists 
believe that the development of human intelligence has been critically dependent 
upon these three factors: Brain volume, brain convolutions, and social interactions 
among individuals. Here we find a class of animals where the three conditions 
leading to human intelligence may be exceeded, and in some cases greatly 

But because whales and dolphins have no hands, tentacles, or other 
manipulative organs, their intelligence cannot be worked out in technology. What 
is left? Payne has recorded examples of very long songs sung by the humpback 
whale; some of the songs were as long as half an hour or more. A few of them 
appear to be repeatable, virtually phoneme by phoneme; somewhat later the 
entire cycle of sounds comes out virtually identically once again. Some of the songs 
have been commercially recorded and are available on CRM Records (SWR-II). I 
calculate that the approximate number of bits (see Chapter 34) of information 
(individual yes/ no questions necessary to characterize the song) in a whale song of 
half an hour's length is between a million and a hundred million bits. Because of 
the very large frequency variation in these songs, I have assumed that the 
frequency is important in the content of the song - or, put another way, that 
whale language is tonal. If it is not as tonal as I guess, the number of bits in such a 
song may go down by a factor of ten. Now, a million bits is approximately the 
number of bits in The Odyssey or the Icelandic Eddas. (It is also unlikely that in 
the few hydrophone forays into Cetacean vocalizations that have been made to 
date, the longest of such songs has been recorded.) 

Is it possible that the intelligence of Cetaceans is channeled into the equivalent 
of epic poetry, history, and elaborate codes of social interaction? Are whales and 
dolphins like human Homers before the invention of writing, telling of great deeds 
done in years gone by in the depths and far reaches of the sea? Is there a kind of 
Moby Dick in reverse - a tragedy, from the point of view of a whale, of a 
compulsive and implacable enemy, of unprovoked attacks by strange wooden and 
metal beasts plying the seas and laden with humans? 

The Cetacea hold an important lesson for us. The lesson is not about whales 
and dolphins, but about ourselves. There is at least moderately convincing 
evidence that there is another class of intelligent beings on Earth besides ourselves. 
They have behaved benignly and in many cases affectionately toward us. We have 
systematically slaughtered them. There is a monstrous and barbaric traffic in the 
carcasses and vital fluids of whales. Oil is extracted for lipstick, industrial 
lubricants and other purposes, even though this makes, at best, marginal economic 
sense - there are effective substitute lubricants. But why, until recently, has there 
been so little outcry against this slaughter, so little compassion for the whale? 

Little reverence for life is evident in the whaling industry - underscoring a 
deep human failing that is, however, not restricted to whales. In warfare, man 
against man, it is common for each side to dehumanize the other so that there will 


be none of the natural misgivings that a human being has at slaughtering another. 
The Nazis achieved this goal comprehensively by declaring whole peoples 
untermenschen, subhumans. It was then permissible, after such reclassification, to 
deprive these peoples of civil liberties, enslave them, and murder them. The Nazis 
are the most monstrous, but not the most recent, example. Many other cases 
could be quoted. For Americans, covert reclassifications of other peoples as 
untermenschen has been the lubricant of military and economic machinery, from 
the early wars against the American Indians to our most recent military 
involvements, where other human beings, military adversaries but inheritors of an 
ancient culture, are decried as gooks, slopeheads, slanteyes, and so on - a litany of 
dehumanization - until our soldiers and airmen could feel comfortable at 
slaughtering them. 

Automated warfare and aerial destruction of unseen targets make such 
dehumanization all the easier. It increases the "efficiency" of warfare because it 
undercuts our sympathies with our fellow creatures. If we do not see whom we 
kill, we feel not nearly so bad about murder. And if we can so easily rationalize 
the slaughter of others of our own species, how much more difficult will it be to 
have a reverence for intelligent individuals of different species? 

It is at this point that the ultimate significance of dolphins in the search for 
extraterrestrial intelligence emerges. It is not a question of whether we are 
emotionally prepared in the long run to confront a message from the stars. It is 
whether we can develop a sense that beings with quite different evolutionary 
histories, beings who may look far different from us, even "monstrous," may, 
nevertheless, be worthy of friendship and reverence, brotherhood and trust. We 
have far to go; while there is every sign that the human community is moving in 
this direction, the question is, are we moving fast enough? The most likely contact 
with extraterrestrial intelligence is with a society far more advanced than we 
(Chapter 31). But we will not at any time in the foreseeable future be in the 
position of the American Indians or the V ietnamese - colonial barbarity practiced 
on us by a technologically more advanced civilization - because of the great spaces 
between the stars and what I believe is the neutrality or benignness of any 
civilization that has survived long enough for us to make contact with it. Nor will 
the situation be the other way around, terrestrial predation on extraterrestrial 
civilizations - they are too far away from us and we are relatively powerless. 
Contact with another intelligent species on a planet of some other star - a species 
biologically far more different from us than dolphins or whales - may help us to 
cast off our baggage of accumulated jingoisms, from nationalism to human 
chauvinism. Though the search for extraterrestrial intelligence may take a very 
long time, we could not do better than to start with a program of rehumanization 
by making friends with the whales and the dolphins. 


Sequence from 2001: A Space Odyuey. Cover picture. The 
Slaking of Kubrick't "2001“ original Signet paperback. 


25. "Hello, Central Casting? Send Me Twenty 

My friend Arthur C. Clarke had a problem. He was writing a major motion 
picture with Stanley Kubrick of Dr. Strangelove fame. It was to be called Journey 
Beyond the Stars, and a small crisis in the story development had arisen. Could I 
have dinner with them at Kubrick's New York penthouse and help adjudicate the 
dispute? (The film's title, by the way, seemed a little strange to me. As far as I 
knew, there is no place beyond the stars. A film about such a place would have to 
be two hours of blank screen - a possible plot only for Andy Warhol. I was sure 
that was not what Kubrick and Clarke had in mind.) 

After a pleasant dinner, the crisis emerged as follows: About midway through 
the movie, a manned space vehicle is making a close approach to either Jupiter 5, 
the innermost satellite of Jupiter, or to Iapetus, one of the middle-sized satellites 
of Saturn. As the spacecraft approaches and the curvature of the satellite is visible 
on the screen, we become aware that the satellite is not a natural moon. It is an 
artifact of some immensely powerful, advanced civilization. Suddenly, an aperture 
appears in the side of the satellite; through it we see - stars. But they are not the 
stars on the other side of the satellite. They are a portion of the sky from 
elsewhere. Small drone rockets are fired into the aperture, but contact with them 
is lost as soon as they pass through. The aperture is a space gate, a way to get from 
one part of the universe to another without the awkwardness of traversing the 
intervening distance. The spacecraft plunges through the gate and emerges in the 
vicinity of another stellar system, with a red giant star blazing in the sky. Orbiting 
the red giant is a planet, obviously the site of an advanced technological 
civilization. The spacecraft approaches the planet, makes landfall, and then - 

Although the human elements were nearing studio production in England, this 
fairly important plot line - the ending! - had not yet been worked out by the two 
authors. The spacecraft's crew, or some fraction of it, was to make contact with 
extraterrestrials. Yes, but how to portray the extraterrestrials? Kubrick favored 
extraterrestrials not profoundly different from human beings. Kubrick's preference 
had one distinct advantage, an economic one: He could call up Central Casting and 
ask for twenty extraterrestrials. With a little makeup, he would have his problem 
solved. The alternative portrayal of extraterrestrials, whatever it was, was bound 
to be expensive. 

I argued that the number of individually unlikely events in the evolutionary 
history of Man was so great that nothing like us is ever likely to evolve again 
anywhere else in the universe. I suggested that any explicit representation of an 
advanced extraterrestrial being was bound to have at least an element of falseness 
about it, and that the best solution would be to suggest, rather than explicitly to 
display, the extraterrestrials. 


The film, subsequently titled 2001: A Space Odyssey, opened three years later. 
At the premiere, I was pleased to see that I had been of some help. As we learn 
from Jerome Agel's book The Making of Kubrick's "2001" (Signet, 1970), Kubrick 
experimented during production with many representations of extraterrestrial life, 
including a pirouetting dancer in black tights with white polka dots. Photographed 
against a black background, this would have been visually very effective. He finally 
decided on a surrealistic representation of extraterrestrial intelligence. The movie 
has played a significant role in expanding the average person's awareness of the 
cosmic perspective. Many Soviet scientists consider 2001 to be the best American 
movie they have seen. The extraterrestrial ambiguities did not bother them at all. 

During the filming of 2001, Kubrick, who obviously has a grasp for detail, 
became concerned that extraterrestrial intelligence might be discovered before the 
$10.5 million film was released, rendering the plot line obsolete, if not erroneous. 
Lloyd's of London was approached to underwrite an insurance policy protecting 
against losses should extraterrestrial intelligence be discovered. Lloyd's of London, 
which insures against the most implausible contingencies, declined to write such a 
policy. In the mid-1960s there was no search being performed for extraterrestrial 
intelligence, and the chance of accidentally stumbling on extraterrestrial 
intelligence in a few years' period was extremely small. Lloyd's of London missed a 
good bet. 


Acom by Jon Lemberg. Tbc faint wisps of bright gas in the 

background are from n supernova remnant. 


26. The Cosmic Connection 

From earliest times, human beings have pondered their place in the universe. 
They have wondered whether they are in some sense connected with the 
awesome and immense cosmos in which the Earth is imbedded. 

Many thousands of years ago a pseudoscience called astrology was invented. 
The positions of the planets at the birth of a child were supposed to play a major 
role in determining his or her future. The planets, moving points of light, were 
thought, in some mysterious sense, to be gods. In his vanity, Man imagined the 
universe designed for his benefit and organized for his use. 

Perhaps the planets were identified with gods because their motions seemed 
irregular. The word "planet" is Greek for wanderer. The unpredictable behavior of 
the gods in many legends may have corresponded well with the apparently 
unpredictable motions of the planets. The argument may have been: Gods don't 
follow rules; planets don't follow rules; planets are gods. 

When the ancient priestly astrological caste discovered that the motions of the 
planets were not irregular but predictable, they seem to have kept this 
information to themselves. No use unnecessarily worrying the populace, 
undermining religious belief, and eroding the supports of political power. 
Moreover, the Sun was the source of life. The Moon, through the tides, dominated 
agriculture - especially in river basins like the Indus, the Nile, the Yangtze, and 
the Tigris- Euphrates. How reasonable that these lesser lights, the planets, should 
have a subtler but no less definite influence on human lifel 

The search for a connection, a hooking-up between people and the universe, 
has not diminished since the dawn of astrology. The same human needs exist 
despite the advances of science. 

We now know that the planets are worlds more or less like our own. We 
know that their light and gravity have negligible influence on a newborn babe. We 
know that there are enormous numbers of other objects - asteroids, comets, 
pulsars, quasars, exploding galaxies, black holes, and the rest — objects not known 
to the ancient speculators who invented astrology. The universe is immensely 
grander than they could have imagined. 

Astrology has not attempted to keep pace with the times. Even the calculations 
of planetary motions and positions performed by most astrologers are usually 

No study shows a statistically significant success rate in predicting through 
their horoscopes the futures or the personality traits of newborn children. There is 
no field of radio-astrology or X-ray astrology or gamma-ray astrology, taking 
account of the energetic new astronomical sources discovered in recent years. 

Nevertheless, astrology remains immensely popular everywhere. There are at 
least ten times more astrologers than astronomers. A large number, perhaps a 
majority, of newspapers in the United States have daily columns on astrology. 


Many bright and socially committed young people have more than a passing 
interest in astrology. It satisfies an almost unspoken need to feel a significance for 
human beings in a vast and awesome cosmos, to believe that we are in some way 
hooked up with the universe - an ideal of many drug and religious experiences, 
the samadhi of some Eastern religions. 

The great insights of modern astronomy have shown that, in some senses quite 
different from those imagined by the earlier astrologers, we are connected up with 
the universe. 

The first scientists and philosophers - Aristotle, for example - imagined that 
the heavens were made of a different sort of material than the Earth, a special kind 
of celestial stuff, pure and undefiled. We now know that this is not the case. 
Pieces of the asteroid belt called meteorites; samples of the Moon returned by 
Apollo astronauts and Soviet unmanned spacecraft; the solar wind, which expands 
outward past our planet from the Sun; and the cosmic rays, which are probably 
generated from exploding stars and their remnants - all show the presence of the 
same atoms we know here on Earth. Astronomical spectroscopy is able to 
determine the chemical composition of collections of stars billions of light-years 
away. The entire universe is made of familiar stuff. The same atoms and molecules 
occur at enormous distances from Earth as occur here within our Solar System. 

These studies have yielded a remarkable conclusion. Not only is the universe 
made everywhere of the same atoms, but the atoms, roughly speaking, are present 
everywhere in approximately the same proportions. 

Almost all the stuff of the stars and the interstellar matter between the stars is 
hydrogen and helium, the two simplest atoms. All other atoms are impurities, 
trace constituents. This is also true for the massive outer planets of our Solar 
System, like Jupiter. But it is not true for the comparatively tiny hunks of rock and 
metal in the inner part of the Solar System, like our planet Earth. This is because 
the small terrestrial planets have gravities too weak to hold their original hydrogen 
and helium atmospheres, which have slowly leaked away to space. 

The next most abundant atoms in the universe turn out to be oxygen, carbon, 
nitrogen, and neon. These are atoms everyone has heard of. Why are the 
cosmically most abundant elements those that are reasonably common on Earth - 
rather than, say, yttrium or praseodymium? 

The theory of the evolution of stars is sufficiently advanced that astronomers 
are able to understand the various kinds of stars and their relations - how a star is 
born from the interstellar gas and dust, how it shines and evolves by 
thermonuclear reactions in its hot interior, and how it dies. These thermonuclear 
reactions are of the same sort as the reactions that underlie thermonuclear 
weapons (hydrogen bombs) : The conversion of four atoms of hydrogen into one of 

But in the later stages of stellar evolution, higher temperatures are reached in 
the insides of stars, and elements heavier than helium are generated by 
thermonuclear processes. Nuclear astrophysics indicates that the most abundant 


atoms produced in such hot red giant stars are precisely the most abundant atoms 
on Earth and elsewhere in the universe. The heavy atoms generated in the insides 
of red giants are spewed out into the interstellar medium, by slow leakage from 
the star's atmosphere like our own solar wind, or by mighty stellar explosions, 
some of which can make a star a billion times brighter than our Sun. 

Recent infrared spectroscopy of hot stars has discovered that they are blowing 
off silicates into space - rock powder spewed out into the interstellar medium. 
Carbon stars probably expel graphite particles into surrounding cosmic space. 
Other stars shed ice. In their early histories, stars like the Sun probably propelled 
large quantities' of organic compounds into interstellar space; indeed, simple 
organic molecules are found by radio astronomical methods to be filling the space 
between the stars. The brightest planetary nebula known (a planetary nebula is an 
expanding cloud usually surrounding an exploding star called a nova) seems to 
contain particles of magnesium carbonate: Dolomite, the stuff of the European 
mountains of the same name, expelled by a star into interstellar space. 

These heavy atoms - carbon, nitrogen, oxygen, silicon, and the rest - then float 
about in the interstellar medium until, at some later time, a local gravitational 
condensation occurs and a new sun and new planets are formed. This second- 
generation solar system is enriched in heavy elements. 

The fate of individual human beings may not now be connected in a deep way 
with the rest of the universe, but the matter out of which each of us is made is 
intimately tied to processes that occurred immense intervals of time and 
enormous distances in space away from us. Our Sun is a second- or third- 
generation star. All of the rocky and metallic material we stand on, the iron in our 
blood, the calcium in our teeth, the carbon in our genes were produced billions of 
years ago in the interior of a red giant star. We are made of star-stuff. 

Our atomic and molecular connection with the rest of the universe is a real and 
unfanciful cosmic hookup. As we explore our surroundings by telescope and space 
vehicle, other hookups may emerge. There may be a network of 
intercommunicating extraterrestrial civilizations to which we may link up 
tomorrow, for all we know. The undelivered promise of astrology - that the stars 
impel our individual characters - will not be satisfied by modern astronomy. But 
the deep human need to seek and understand our connection with the universe is 
a goal well within our grasp. 


t y. Extraterrestrial Life: An Idea Whose Time Has 


Thousands of years ago, the idea that the planets were populated by intelligent 
beings was uncommon. The idea was that the planets themselves were intelligent 
beings. Mars was the god of war, Venus was the goddess of beauty, Jupiter was the 
king of the gods. 

In early Roman times a few writers, for example Lucian of Samasota, conceived 
that at least the Moon was a place that was populated as the Earth was. His 
science-fiction story describing travel to the Moon was called the "True History." 
It was, of course, false. 

The idea of the planets as an elegant celestial clockwork created by the Deity 
for the amazement and utility of men emerged in the Renaissance. In the year 
1600 Giordano Bruno was burned to death at the stake, in part for uttering and 
publishing the heresy that there were other worlds and other beings inhabiting 

The pendulum swung far in the other direction in subsequent centuries. 
Writers such as Bernard de Fontenelle, Emanuel Swedenborg, and even Immanuel 
Kant and Johannes Kepler could safely imagine that perhaps all the planets were 
inhabited. Indeed, the idea was expressed that the name of the planet gave some 
hint to the character of its inhabitants. The denizens of Venus were amorous; 
those of Mars, warlike or martial; the inhabitants of Mercury, fickle or mercurial; 
those of Jupiter, jolly or jovial. And so on. The great British astronomer William 
Herschel even supposed that the Sun was inhabited. 

But as the extremes of the physical environments in the Solar System became 
clearer and the exquisite adaptation to the environment of organisms on Earth 
became more apparent, skeptics arose. Perhaps Mars and Venus were inhabited, 
but surely not Mercury, not the Moon, not Jupiter. And so on. 

In the last few decades of the nineteenth century the observations of the planet 
Mars by Giovanni Schiaparelli and Percival Lowell quickened public excitement 
about the possibility of intelligence on our planetary neighbor. Lowell's passion for 
the idea of intelligent beings on Mars, his articulateness, and the wide publication 
of his books did much to bring this idea to the public attention, as did science- 
fiction writers who followed the Lowellian scenario. 

But as the evidence for intelligent life on Mars withered, and as the 
environment of Mars was perceived to be more and more inclement by terrestrial 
standards, popular enthusiasm for the idea waned. 

By then, scientific interest in extraterrestrial life had reached a nadir. The very 
enthusiasm with which Lowell pursued the idea of intelligent beings on Mars and 
the attention that these ideas received from the man in the street repelled many 
scientists. In addition, a new astronomical field, astrophysics, the application of 
physics to the surfaces and interiors of stars, had achieved phenomenal success, 

and the brightest and most enthusiastic young astronomers went into stellar 
astronomy rather than planetary studies. The pendulum had swung so far that in 
the period just after the Second World War, there was - in all of the United States 
- only one astronomer doing serious physical investigations of the planets, G. P. 
Kuiper, then of the University of Chicago. Not only had astronomers been turned 
off extraterrestrial life, they had been turned off planetary studies in general. 

Since 1950, the situation has slowly reversed again; the pendulum is once more 
swinging. The development of new measuring instruments (a by-product of 
World War II), at first ground-based and then, more important, space-borne, has 
produced a massive infusion of basic new knowledge about the physical 
environments of the Moon and planets. Young scientists have again been attracted 
to planetary studies, not only astronomers, but also geologists, chemists, physicists, 
and biologists. The discipline needs them all. 

We now know that the building blocks for the origin of life are in the cards of 
physics and chemistry; whenever standard primitive atmospheres are exposed to 
common energy sources, the building blocks of life on Earth drop out of the 
atmosphere in times of days or weeks. Organic compounds have been found in 
meteorites and in interstellar space. Small quantities have been found even in such 
an inhospitable environment as the Moon. They are suspected to exist in Jupiter, 
in the outer planets of the Solar System, as well as on Titan, the largest moon of 
Saturn. Both theory and observation now suggest that planets are a common, if not 
invariable, accompaniment of stars, rather than an exceedingly rare occurrence, as 
was fashionable to believe in the first decades of this century (see pages 192 and 

o* u 100 It 000} 



I 15 f f | f I jf 

_| 1 — 1...L I I 111 

J 1 L 1 1.1-1. 

_i — i i i mil 

The Solar System. Distances from the Sun arc shown in units 
of the Earths distance. The trident markings are a sign 
of the eccentricity of a planetary orbit and show the clos- 
est. farthest, and average distance of the planet from the 
Sun. The masses of the planets are shown in units of the 
Earth’s mass. The ]ovian planets are distinguished from the 
terrestrial pluncts by cross-hatching. 


Five itokItI solar systems derived by Steven Dole in a com- 
puter experiment on the physics of the origins of solar sys- 
tems. Dole's systems are clearly very similar to our Solar Sys- 
tem. This is one of several lines of evidence suggesting that 
planetary systems are common accompaniments of stars 
throughout the Calaxv. Courtesy. ICARUS. 

W e now have, for the first time, the tools to make contact with civilizations on 
planets of other stars. It is an astonishing fact that the great one-thousand-foot- 
diameter radio telescope of the National Astronomy and Ionosphere Center, run 
by Cornell University in Arecibo, Puerto Rico, would be able to communicate 
with an identical copy of itself anywhere in the Milky Way Galaxy. We have at 
our command the means to communicate not merely over distances of hundreds 
or thousands of light-years; we can communicate over tens of thousands of light- 
years, into a volume containing hundreds of billions of stars. The hypothesis that 
advanced technical civilizations exist on planets of other stars is amenable to 
experimental testing. It has been removed from the arena of pure speculation. It is 
now in the arena of experiment. 

Our first attempt to listen to broadcasts from extraterrestrial societies was 
Project Ozma. Organized by Frank Drake in i960 at the National Radio 
Astronomy Observatory (NR AO), it looked at two stars at one frequency for two 


weeks. The results were negative. Slightly more ambitious projects are, at the time 
of writing, being performed at the Gorky Radiophysical Institute in the Soviet 
Union and at NRAO in the United States. All in all, perhaps a few hundred 
nearby stars will be examined at one or two frequencies. But even the most 
optimistic calculations on the distances to the nearest stars suggest that hundreds 
of thousands to millions of stars must be examined before an intelligible signal 
from one of them will be received. This requires a large effort covering a sizable 
period of time. But it is well within our resources, our abilities, and our interests. 

The change in the climate of opinion about extraterrestrial life was reflected in 
1971 by a scientific conference held in Byurakan, Soviet Armenia, and sponsored 
jointly by the Soviet Academy of Sciences of the U.S.S.R. and the National 
Academy of Sciences of the United States. I had the privilege of chairing the U.S. 
delegation to this meeting. The participants represented astronomy, physics, 
mathematics, biology, chemistry, archaeology, anthropology, history, electronics, 
computer technology, and cryptography. The group, which included two skeptical 
Nobel laureates, was marked for its crossing of national as well as disciplinary 
boundaries. The conference concluded that the chances of there being 
extraterrestrial communicative societies and our present technological ability to 
contact them were both sufficiently high that a serious search was warranted. 
Some of the specific conclusions that were reached were these: 

1. The striking discoveries of recent years in the fields of astronomy, biology, 
computer science and radiophysics have transferred some of the problems of 
extraterrestrial civilizations and their detection from the realm of speculation to a 
new realm of experiment and observation. For the first time in human history, it 
has become possible to make serious and detailed experimental investigations of 
this fundamental and important problem. 

2. This problem may prove to be of profound significance for the future 
development of Mankind. If extraterrestrial civilizations are ever discovered, the 
affect on human scientific and technological capabilities will be immense, and the 
discovery can positively influence the whole future of Man. The practical and 
philosophical significance of a successful contact with an extraterrestrial 
civilization would be so enormous as to justify the expenditure of substantial 
efforts. The consequences of such a discovery would greatly add to the total of 
human knowledge. 

3. The technological and scientific resources of our planet are already large 
enough to permit us to begin investigations directed towards the search for 
extraterrestrial intelligence. As a rule, such studies should provide important 
scientific results even when specific searches for extraterrestrial intelligence do not 
succeed. At present, these investigations can be carried out effectively in the 
various countries by their own scientific institutions. Even at this early stage, 
however, it would be useful to discuss and coordinate specific programs of 
research and to exchange scientific information. In the future, it would be 
desirable to combine the efforts of investigators in various countries to achieve the 


experimental and observational objectives. It seems to us appropriate that the 
search for extraterrestrial intelligence should be made by representatives of the 
whole of mankind. 

4. Various modes of search for extraterrestrial intelligence were discussed in 
detail at the Conference. The realization of the most elaborate of these proposals 
would require considerable time and effort and an expenditure of funds 
comparable to the funds devoted to space and nuclear research. Useful searches 
can, however, also be initiated at a very modest scale. 

5. The Conference participants consider highly valuable present and 
forthcoming space-vehicle experiments directed towards searching for life on the 
other planets of our solar system. They recommend the continuation and 
strengthening of work in such areas as prebiological organic chemistry, searches for 
extrasolar planetary systems, and evolutionary biology, which bear sharply on the 

6. The Conference recommends the initiation of specific new investigations 
directed towards modes of search for signals. 

(The complete Proceedings of the conference are published as Communication 
with Extraterrestrial Intelligence, Carl Sagan, ed., Cambridge, Massachusetts, The 
M.I.T. Press, 1973.) 

Another sign of the increasing acceptability of the search for extraterrestrial 
intelligence is the recommendations of the Astronomy Survey Committee of the 
U. S. National Academy of Sciences, which had been asked to summarize the 
needs of astronomy in the decade of the 1970s. The Committee's report was the 
first such national report on the future of astronomy to lay stress on the search for 
extraterrestrial intelligence - as a possibly important by-product of astronomical 
research in the near future and as a justification for the construction of large radio 

Nearer to home, there is an accelerating set of laboratory studies of the origin 
of life on Earth. If the origin of life on Earth turns out to have been exceedingly 
"easy," the chances of life elsewhere are correspondingly high. 

There is also a concerted effort in the United States - Project Viking - to land 
instrumented payloads on the surface of Mars to search for indigenous life forms. 

The idea of extraterrestrial life is an idea whose time has come. 


28. Has the Earth Been Visited? 

By far the cheapest way of communicating with the Earth, if you're a 
representative of an advanced extraterrestrial civilization, is by radio. A single bit 
of radio information, sent winging across space to the Earth, would cost far less 
than a penny. A radio search for extraterrestrial intelligence seems, therefore, a 
very reasonable place for us to begin. But should we not examine other 
possibilities closer to home? Wouldn't we look silly if we expended a major effort 
listening for radio messages or searching for life on Mars if, all the while, there was 
here on Earth evidence of extraterrestrial life? 

There are two hypotheses of this sort that have gained a following in the 
popular literature. The first postulates that the Earth is today being visited by 
spacecraft from other worlds - this is the extraterrestrial flying saucer or 
unidentified flying object (UFO) hypothesis. The second also postulates that the 
Earth has been visited by such spacecraft, but in the past, before written history. 

The extraterrestrial hypothesis of UFO origins is a complex subject, powerfully 
dependent on the reliability of witnesses. A comprehensive discussion of this 
problem has recently been published in UFO's: A Scientific Debate (Carl Sagan and 
Thornton Page, editors, Ithaca, N.Y., Cornell University Press, 1972), in which all 
sides of the subject have been aired. My own view is that there are no cases that 
are simultaneously very reliable (reported independently by a large number of 
witnesses) and very exotic (not explicable in terms of reasonably postulated 
phenomena - as a strange moving light could be a searchlight from a weather 
airplane or a military aerial refueling operation). There are no reliably reported 
cases of strange machines landing and taking off, for example. 

There is another approach to the extraterrestrial hypothesis of UFO origins. 
This assessment depends on a large number of factors about which we know little, 
and a few about which we know literally nothing. I want to make some crude 
numerical estimate of the probability that we are frequently visited by 
extraterrestrial beings. 

Now, there is a range of hypotheses that can be examined in such a way. Let 
me give a simple example: Consider the Santa Claus hypothesis, which maintains 
that, in a period of eight hours or so on December 24-25 of each year, an out-sized 
elf visits one hundred million homes in the United States. This is an interesting 
and widely discussed hypothesis. Some strong emotions ride on it, and it is argued 
that at least it does no harm. 

We can do some calculations. Suppose that the elf in question spends one 
second per house. This isn't quite the usual picture - "Ho, Ho, Ho," and so on - 
but imagine that he is terribly efficient and very speedy; that would explain why 
nobody ever sees him very much - only one second per house, after all. With a 
hundred million houses he has to spend three years just filling stockings. I have 
assumed he spends no time at all in going from house to house. Even with 
relativistic reindeer, the time spent in a hundred million houses is three years and 


not eight hours. This is an example of hypothesis-testing independent of reindeer 
propulsion mechanisms or debates on the origins of elves. We examine the 
hypothesis itself, making very straightforward assumptions, and derive a result 
inconsistent with the hypothesis by many orders of magnitude. We would then 
suggest that the hypothesis is untenable. 

We can make a similar examination, but with greater uncertainty, of the 
extraterrestrial hypothesis that holds that a wide range of UFOs viewed on the 
planet Earth are space vehicles from planets of other stars. The report rates, at 
least in recent years, have been several per day, at the very least. I will not make 
that assumption. I will make the much more conservative assumption that one 
such report per year corresponds to a true interstellar visitation. Let's see what this 

We have to have some feeling for the number, N, of extant technical 
civilizations in the Galaxy - that is, civilizations vastly in advance of our own, 
civilizations that are able, by whatever means, to perform interstellar space flight. 
(While the means are difficult, they don't enter into this discussion, just as 
reindeer propulsion mechanisms don't affect our discussion of the Santa Claus 

An attempt has been made to specify explicitly the factors that enter a 
determination of the number of such technical civilizations in the Galaxy. I will 
not here run through what numbers have been assigned to the various quantities 
involved — it's a multiplication of many probabilities, and the likelihood that we 
can make a good judgment decreases as we proceed down the list. N depends first 
on the mean rate at which stars are formed in the Galaxy, a number that is known 
reasonably well. It depends on the number of stars that have planets, which is less 
well known, but there are some data on that. It depends on the fraction of such 
planets that are so suitably located with respect to their star that the environment 
is a feasible one for the origin of life. It depends on the fraction of such otherwise 
feasible planets on which the origin of life, in fact, occurs. It depends on the 
fraction of those planets on which the origin of life occurs in which, after life has 
arisen, an intelligent form comes into being. It depends on the fraction of those 
planets in which intelligent forms have arisen that evolve a technical civilization 
substantially in advance of our own. And it depends on the average lifetime of 
such a technical civilization. 

It is clear that we are rapidly running out of examples as we go farther and 
farther along. We have many stars, but only one instance of the origin of life, and 
only a very limited number - some would say only one - of instances of the 
evolution of intelligent beings and technical civilizations on this planet. And we 
have no cases whatever to make a judgment on the mean lifetime of a technical 
civilization. Nevertheless, there is an entertainment that some of us have been 
engaged in, making our best estimates about these numbers and coming out with a 
value of N. The result that emerges is that N roughly equals one tenth the average 
lifetime of a technical civilization in years. 

1 57 

If we put in a number like ten million (10 7 ) years for the average lifetime of 
advanced technical civilizations, we come out with a number for such technical 
civilizations in the Galaxy of about a million (io 6 ) - that is, a million other stars 
with planets on which today there are advanced civilizations. This is quite a 
difficult calculation to do accurately. The choice of ten million years for the 
average lifetime of a technical civilization is rather optimistic. But let's take these 
optimistic numbers and see where they lead us. 

Let's assume that each of these million technical civilizations launches Q 
interstellar space vehicles a year, so that io 6 Q interstellar space vehicles are 
launched per year. Let's assume that there's only one contact made per journey. In 
the steady-state situation, there are something like io 6 Q arrivals somewhere or 
other per year. Now, there surely are something like 10 10 interesting places in the 
Galaxy to go visit (we have several times 10 11 stars) and, therefore, an average of 
i/io 4 =io -4 arrivals at a given interesting place (let's say a planet) per year. So if 
only one UFO is to visit the Earth each year, we can calculate what mean launch 
rate is required at each of these million worlds. The number turns out to be ten 
thousand launches per year per civilization, and ten billion launches in the Galaxy 
per year. This seems excessive. Even if we imagine a civilization much more 
advanced than ours, to launch ten thousand such vehicles for only one to appear 
here is probably asking too much. And if we were more pessimistic on the 
lifetime of advanced civilizations, we would require a proportionately larger 
launch rate. But as the lifetime decreases, the probability that a civilization would 
develop interstellar flight very likely decreases as well. 

There is a related point made by the American physicist Hong-Yee Chiu; he 
takes more than one UFO arriving at Earth per year, but his argument follows 
along the same lines as the one I have just presented. He calculates the total mass 
of metals involved in all of these space vehicles during this history of the Galaxy. 
The vehicle has to be of some size - it should be bigger than the Apollo capsule, 
let's say - and we can calculate how much metal is required. It turns out that the 
total mass of half a million stars has to be processed and all their metals extracted. 
Or if we extend the argument and assume that only the outer few hundred miles 
or so of stars like the Sun can be mined by advanced technologies (farther in, it's 
too hot), we find that two billion such stars must be processed, or about 1 percent 
of the stars in the Galaxy. This also sounds unlikely. 

Now you may say, "Well, that's a very parochial approach; maybe they have 
plastic spaceships." Yes, I suppose that's possible. But the plastic has to come from 
somewhere, and plastics vs. metals changes the conclusions very little. This 
calculation gives some feeling for the magnitude of the task when we are asked to 
believe that there are routine and frequent interstellar visits to our planet. 

What about possible counterarguments? For example, it might be argued that 
we are the object of special attention - we have just developed all sorts of signs of 
civilization and high intelligence like nuclear weapons, and maybe, therefore, we 
are of particular interest to interstellar anthropologists. Perhaps. But we have only 


signaled the presence of our technical civilization in the past few decades. The 
news can be only some tens of light-years from us. Also, all the anthropologists in 
the world do not converge on the Andaman Islands because the fish net has just 
been invented there. There are a few fish net specialists and a few Andaman 
specialists; and these guys say, "Well, there's something terrific going on in the 
Andaman Islands. I've got to spend a year there right away because if I don't go 
now, I'll miss out." But the pottery experts and the specialists in Australian 
aborigines don't pack up their bags and leave for the Indian Ocean. 

To imagine that there is something absolutely fascinating about what is 
happening right here is precisely contrary to the idea that there are lots of 
civilizations around. Because if the latter is true, the development of our sort of 
civilization must be pretty common. And if we are not pretty common, then there 
are not going to be many civilizations advanced enough to send visitors. 

Even so, is it not possible that the second UFO hypothesis is true - that in 
historical or recent prehistoric times an extraterrestrial space vehicle made landfall 
on Earth? There is surely no way in which we can exclude such a contingency. 
How could we prove it? 

A number of popular books have recently been written that allege to 
demonstrate such a visitation. The arguments are of two sorts, legend and artifact. 
I broached this subject in the book Intelligent Life in the Universe, written with the 
Soviet astrophysicist I. S. Shklovskii and published in 1966. I examined a typical 
legend suggestive of contact between our ancestors and an apparent representative 
of a superior society. The legend, taken from the earliest Sumerian mythology, is 
important because the Sumerians are the direct cultural antecedents of our own 
civilization. A superior being was supposed to have taught the Sumerians 
mathematics, astronomy, agriculture, social and political organization, and written 
language — all the arts necessary for making the transition from a hunter-gatherer 
society to the first civilization. 

But as provocative as this and similar legends were, I concluded that it was 
impossible to demonstrate extraterrestrial contact from such legends: There are 
plausible alternative explanations. We can understand why priests might make 
myths about superior beings who inhabit the skies and give directions to human 
beings on how to order their affairs. Among other "advantages," such legends 
permit the priests to control the people. 

There is only one category of legend that would be convincing: When 
information is contained in the legend that could not possibly have been generated 
by the civilization that created the legend - if, for example, a number transmitted 
from thousands of years ago as holy turns out to be the nuclear fine structure 
constant. This would be a case worthy of some considerable attention. 

Also convincing would be a certain class of artifact. If an artifact of technology 
were passed on from an ancient civilization - an artifact that is far beyond the 
technological capabilities of the originating civilization - we would have an 
interesting prima facie case for extraterrestrial visitation. An example would be an 


illuminated manuscript, rescued from an Irish monastery, that contains the 
electronic circuit diagram for a superheterodyne radio receiver. Great care would 
have to be taken about the provenance of this artifact, just as art collectors are 
cautious about a newly discovered Raphael. We would make sure that no 
contemporary Irish prankster was the source of the circuit diagram. 

To the best of my knowledge, there are no such legends and no such artifacts. 
All the ancient artifacts put forward, for example, by Erik von Danniken in his 
book Chariots of the Gods ? have a variety of plausible, alternative explanations. 
Representations of beings with large, elongated heads, alleged to resemble space 
helmets, could equally well be inelegant artistic renditions, depictions of 
ceremonial head masks or expressions of rampant hydrocephalia. In fact, the 
expectation that extraterrestrial astronauts would look precisely like American or 
Soviet astronauts, down to their space suits and eyeballs, is probably less credible 
than the idea of a visitation itself. Likewise, the idea expressed by von Danniken 
and others that ancient astronauts erected airfields, employed rockets, and 
exploded nuclear weapons on Earth is implausible in the extreme, precisely 
because we ourselves have just developed this technology. A visitor from space 
will not be so close to us in time. It is as if, framing such an idea in 1870, we 
concluded that extraterrestrials use hot-air balloons for space exploration. Far 
from being too daring, such ideas are stodgy in their unimaginativeness. Most 
popular accounts of alleged contact with extraterrestrials are strikingly 

An American author named Richard Shaver claims that ordinary rocks, sliced 
fine, contain a set of still photographs left by an ancient civilization, which can be 
run as a movie film. Just pick up any rock and slice it fine, he says. 

In the great high plain of Nasca in Peru, there is a set of enormous geometrical 
figures. They are quite difficult to discern when standing among them, but quite 
discernible from the air. It is easy to see how an early human civilization could 
have made such figures. But why, it is asked, should such constructs be made 
except for or by an extraterrestrial civilization? If people believe in the existence 
of gods in the sky, it is not straining credulity to imagine them making messages to 
communicate with those gods. The markings may be a kind of collective graphical 
prayer. But they do not necessarily demonstrate the reality of the intended 
recipient of the prayer. 

There are other cases that seem to be quite convincing at first, such as a 
perfectly machined steel cube, said to reside in the Salzburg Museum and to have 
been recovered from geological strata millions of years old, or the receipt of the 
television call signals of a television station off the air for three years. These cases 
are almost certainly hoaxes. 

There are equally provocative archaeological circumstances that the writers of 
such sensational books have somehow missed. For example, in the frieze of the 
great Aztec pyramids at San Juan Teotihuacan, outside Mexico City, there is a 
repeated figure, described as a rain god, but looking for all the world like an 


amphibious tracked vehicle with four headlights (see page 201). I do not for a 
moment believe that such amphibious vehicles were indigenous in Aztec times - 
among other reasons, because they are too close to what we have today rather 
than too far from it 

The rain god, on the frieze of the Temple of the Sun, at San 
Juan Teotihuacdn, Mexico. Photogruph by the author. 

These artifacts are, in fact, psychological projective tests. People can see in 
them what they wish. There is nothing to prevent anyone from seeing signs of past 
extraterrestrial visitations all about him. But to a person with an even mildly 
skeptical mind, the evidence is unconvincing. Because the significance of such a 
discovery would be so enormous, we must employ the most critical reasoning and 
the most skeptical attitudes in approaching such data. The data do not pass such 
tests. Pondering wall paintings, for this purpose, like looking for UFOs, remains an 
unprofitable investment of terrestrial intelligence - if we are truly interested in the 
quest for extraterrestrial intelligence. 


ig. A Search Strategy for Detecting Extraterrestrial 


Suppose we have arranged a meeting at an unspecified place in New York City 
with a stranger we have never met and about whom we know nothing - a rather 
foolish arrangement, but one that is useful for our purposes. We are looking for 
him, and he is looking for us. What is our search strategy? We probably would not 
stand for a week on the corner of Seventy-eighth Street and Madison Avenue. 
Instead, we would recall that there are a number of widely known landmarks in 
New York City - as well known to the stranger as to us. He knows we know 
them, we know he knows we know them, and so on. We then shuttle among 
these landmarks: The Statue of Liberty, the Empire State Building, Grand Central 
Station, Radio City Music Hall, Lincoln Center, the United Nations, Times Square, 
and just conceivably, City Hall. We might even indulge ourselves in a few less 
likely possibilities, such as Yankee Stadium or the Manhattan entrance to the 
Staten Island Ferry. But there are not an infinite number of possibilities. There are 
not millions of possibilities; there are only a few dozen possibilities, and in time 
we can cover them all. 

The situation is just the same in the frequency-search strategy for interstellar 
radio communication. In the absence of any prior contact, how do we know 
precisely where to search? How do we know which frequency or "station" to tune 
in on? There are at least millions of possible frequencies with reasonable radio 
bandpasses. But a civilization interested in communicating with us shares with us a 
common knowledge about radio astronomy and about our Galaxy. They know, for 
example, that the most abundant atom in the universe, hydrogen, characteristically 
emits at a frequency of 1,420 Megahertz. They know we know it. They know we 
know they know it. And so on. There are a few other abundant interstellar 
molecules, such as water or ammonia, which have their own characteristic 
frequencies of emission and absorption. Some of these lie in a region of the galactic 
radio spectrum where there is less background noise than others. This is also 
shared information. Students of this problem have come up with a short list of 
possibly a dozen frequencies that seem to be the obvious ones to examine. It is 
even conceivable that water-based life will communicate at water frequencies, 
ammonia-based life at ammonia frequencies, etc. 

There appears to be a fair chance that advanced extraterrestrial civilizations are 
sending radio signals our way, and that we have the technology to receive such 
signals. How should a search for these signals be organized? Existing radio 
telescopes, even very small ones, would be adequate for a preliminary search. 
Indeed, the ongoing search at the Gorky Radiophysical Institute, in the Soviet 
Union, involves telescopes and instrumentation that are quite modest by 
contemporary standards. 


The amiable and capable president of the Soviet Academy of Sciences, M. V. 
Keldysh, once told me, with a twinkle in his eye, that "when extraterrestrial 
intelligence is discovered, then it will become an important scientific problem." A 
leading American physicist has argued forcefully with me that the best method to 
search for extraterrestrial intelligence is simply to do ordinary astronomy; if the 
discovery is to be made, it will be made serendipitously. But it seems to me that 
we can do something to enhance the likelihood of success in such a search, and 
that the ordinary pursuit of radio astronomy is not quite the same as an explicit 
search of certain stars, frequencies, bandpasses, and time constants for 
extraterrestrial intelligence. 

But there are enormous numbers of stars to investigate, and many possible 
frequencies. A reasonable search program will almost certainly be a very long one. 
Such a search, using a large telescope full time, should take at least decades, by 
conservative estimates. The radio observers in such an enterprise, no matter how 
enthusiastic they may be about the search for extraterrestrial intelligence, would 
very likely become bored after many years of unsuccessful searching. A radio 
astronomer, like any other scientist, is interested in working on problems that have 
a high probability of more immediate results. 

The ideal strategy would involve a large telescope that could devote something 
like half time to the search for extraterrestrial intelligent radio signals and about 
half time to the study of more conventional radioastronomical objectives, such as 
planets, radio stars, pulsars, interstellar molecules, and quasars. The difficulty in 
using several existing radio observatories, each for, say, 1 percent of their time, is 
that these activities would have to be pursued for many centuries to have a 
reasonable probability of success. Since the time on existing radio telescopes is 
mainly spoken for, larger allocations of time seem unlikely. 

A wide variety of objects obviously should be examined: G-type stars, like our 
own; M-type stars, which are older; and exotic objects, which may be black holes 
or possible manifestations of astroengineering activities. The number of stars and 
other objects in our own Milky Way Galaxy is about two hundred billion, and the 
number that we must examine to have a fair chance of detecting such signals 
seems to be at least millions. 

There is an alternative strategy to searching painfully each of millions of stars 
for the signals from a civilization not much more advanced than our own. We 
might examine an entire galaxy all at once for signals from civilizations much 
more advanced than ours (see Chapters 34 and 35). A small radio telescope can 
point at the nearest spiral galaxy to our own, the great galaxy M31 in the 
constellation Andromeda, and simultaneously observe some two hundred billion 
stars. Even if many of these stars were broadcasting with a technology only slightly 
in advance of our own, we would not pick them up. But if only a few are 
broadcasting with the power of a much more advanced civilization, we would 
detect them easily. In addition to examining nearby stars only slightly in advance 
of us, it therefore makes sense to examine, simultaneously, many stars in 


neighboring galaxies, only a few of which may have civilizations greatly in advance 
of our technology. 

We have been describing a search for signals beamed in our general direction 
by civilizations interested in communicating with us. We ourselves are not 
beaming signals in the direction of some specific other star or stars. If all 
civilizations listened and none transmitted, we would each reach the erroneous 
conclusion that the Galaxy was unpopulated, except by ourselves. Accordingly, it 
has been proposed — as an alternative and much more expensive enterprise - that 
we also "eavesdrop"; that is, tune in on the signals that a civilization uses for its 
own purposes, such as domestic radio and television transmission, radar 
surveillance systems, and the like. A large radio telescope devoting half time to a 
rigorous search for intelligent extraterrestrial signals beamed our way would cost 
tens of millions of dollars (or rubles) to construct and operate. An array of large 
radio telescopes, designed to eavesdrop to a distance of some hundreds of light- 
years, would cost many billions of dollars. 

In addition, the chance of success in eavesdropping may be slight. One hundred 
years ago we had no domestic radio and television signals leaking out into space. 
One hundred years from now the development of tight beam transmission by 
satellites and cable television and new technologies may mean that again no radio 
and television signals would be leaking into space. It may be that such signals are 
detectable only for a few hundred years in the multibillion-year history of a planet. 
The eavesdropping enterprise, in addition to being expensive, may also have a very 
small probability of success. 

The situation we find ourselves in is rather curious. There is at least a fair 
probability that there are many civilizations beaming signals our way. We have the 
technology to detect these signals out to immense distances - to the other side of 
the Galaxy. Except for a few back-burner efforts in the United States and the 
Soviet Union, we — that is, mankind - are not carrying out the search for 
extraterrestrial intelligence. Such an enterprise is sufficiently exciting and, at last, 
sufficiently respectable that there would be little difficulty in staffing a radio 
observatory designed for this purpose with devoted, capable, and innovative 
scientists. The only obstacle appears to be money. 

While not small change, some tens of millions of dollars (or rubles) is, 
nevertheless, an amount of money well within the reach of wealthy individuals 
and foundations. In fact, there is in astronomy a long and proud history of 
observatories funded by private individuals and foundations: The Lick 

Observatory, on Mount Hamilton, California, by Mr. Lick (who wanted to build a 
pyramid, but settled for an observatory - in the base of which he is buried); the 
Yerkes Observatory in Williams Bay, Wisconsin, by Mr. Yerkes; the Lowell 
Observatory in Llagstaff, Arizona, by Mr. Lowell; and the Mount Wilson and 
Mount Palomar Observatories in Southern California, by a foundation established 
by Mr. Carnegie. Government money will probably be forthcoming for such an 
enterprise eventually. After all, it costs about the same as the replacement costs of 


U.S. aircraft shot down over Vietnam in Christmas week, 1972. But a radio 
telescope designed for communication with extraterrestrial intelligence and an 
attached institute of exobiology would make a very fitting personal memorial for 


A net of intercommunicating galactic civilizations. By Jon 


30. If We Succeed 

In considering the problem of interstellar communication, some people are 
worried. What if a civilization we come into contact with is more advanced than 

The history of contact between advanced and backward technological 
civilizations on Earth is a sorry one. The technically less advanced societies - 
although they may have superior mathematics or astronomy or poetry or moral 
precepts - get wiped out. If this is a law of societal natural selection here, why not 
elsewhere? And in that case, should we not keep quiet? 

There are those who predict a dire catastrophe if we broadcast our presence to 
another star. The extraterrestrials will come and - eat us, or something equally 
unpleasant. (Actually, if we are especially tasty, they need only sample one of us, 
determine what sequence of our amino acids makes us appetizing, and then 
reconstruct the relevant proteins on their own planet. The high freightage makes 
us economically, if not gastronomically, unappetizing.) The message aboard Pioneer 
io was criticized by a few because it "gave away" our position in the Galaxy. I very 
much doubt if we pose any threat to anybody out there. We are the most 
backward possible civilization able to engage in communication, and the vast 
spaces between the stars are a kind of natural quarantine, preventing us at any 
time in the near future from messing around out there. 

But, in any case, it is too late. We have already announced our presence. The 
initial radio broadcasts, starting with Marconi and reaching significant intensity in 
the 1920s, have leaked through the ionosphere and are expanding at the velocity of 
light in a spherical wavefront centered around the Earth. And in that wavefront, 
an advanced technical civilization can pick up the tinny transmissions of Enrico 
Caruso arias, the Scopes trial, the 1928 election returns, the big jazz bands. These 
are the harbingers of the cultures of Earth, our first emissaries to the stars. 

If there are technical civilizations some fifty light-years out, they will just now 
be detecting these strange, primitive signals. Even if they are poised to respond 
instantly with the fastest spaceship possible, it will be at least another fifty years 
before we hear from them. Pioneer 10 will take a million years to cover the same 

It is too late to be shy and hesitant. We have announced our presence to the 
cosmos - in a backward and groping and unrepresentative manner, to be sure - 
but here we arel 

The vast distances between the stars imply that there will be no cosmic 
dialogues by radio transmission. Suppose we receive a signal from a civilization at 
some likely distance for first contact, such as three hundred light-years. The 
message says, perhaps, "Hello, you guys; how are you?" Having long been prepared 
for this moment, we immediately reply, let us say, "Fine, how are you?" The total 
round-trip communication time would be six hundred years. It's not what you'd 
call a snappy conversation. 


Six hundred years ago, the Black Death stalked Europe, the Ming dynasty was 
just founded, Charles the Wise sat on the French throne, Gregory XI was Pope, 
and the Aztecs were hanging those who polluted the water and the air. Six 
hundred years is a long time on Earth. Interstellar radio communication will not be 
a dialogue. It will be a monologue. The dumb guys hear from the smart guys, as if 
the astrologer of Charles the W ise were to receive a message from us. 

While the time for radio signals to travel a distance of three hundred light-years 
is three hundred years, the amount of information that can be conveyed is 
enormous. In fact, with instrumentation not very much more advanced than our 
own, essentially all the important insights of our civilization could be transmitted 
in a few days. It would take three hundred years to get there, but only a few days 
to be transmitted. But the more lively transmission is in the other direction, from 
the smarts (them] to the dumbs (us) (see Chapter 31]. It is possible that there is a 
breath-taking repository of galactic knowledge being beamed from several 
directions at Earth at this moment, advanced text interspersed with primers, so we 
can learn Galactic, the language of transmission. But we will not hear it if we do 
not listen for it. 

But how could we possibly decode such a message? European scholars spent 
more than a century in entirely erroneous attempts to decode Egyptian 
hieroglyphics before the discovery of the Rosetta Stone and the brilliant attack on 
its translation by Young and Champollion. Some ancient languages, such as the 
glyphs of Easter Island, the writings of the Mayas, and some varieties of Cretan 
script, remain completely undecoded to the present time. Y et they were languages 
of human beings like ourselves, with common biological instincts and encodings, 
and distant from us in time by only a few hundreds to a few thousands of years. 
How can we expect that a civilization vastly more advanced than we, and based 
entirely upon different biological principles, could ever send a message we could 

The differences in the two cases are intent and intelligence. The objective of 
the Easter Island glyphs was not to communicate to twentieth-century scientists. It 
was to communicate to other Easter Island inhabitants, or, possibly, to the gods. 
The idea of a code, at least in the usual military intelligence application, is to make 
a message difficult to read. But the situation we are considering is the opposite. 
We are considering not cryptography, but anticryptography, the design by a very 
intelligent civilization of a message so simple that even civilizations as primitive as 
ours can understand it. 

The message will be based upon commonalities between the transmitting and 
receiving civilizations. Those commonalities are, of course, not any spoken or 
written language or any common, instinctual encoding in our genetic materials, but 
rather what we truly share in common - the universe around us, science and 
mathematics. There are schemes in which mathematical propositions are 
transmitted, conveying such concepts as addition and equality and negation and 
then working up to more sophisticated concepts. There are schemes in which 


radio messages are sent, which, from the number of constituent bits, are clearly 
pictures; when reconstructed as pictures, they can be clearly understood. The 
plaque on Pioneer io is an example of a sort of picture which, transmitted as an 
object on a spacecraft or as a picture by radio transmission, would be reliably 
understood by an advanced extraterrestrial civilization. Likewise, similar messages, 
coming our way, will be understood by us, if we have the wit to listen. 

Some individuals find the absence of a dialogue distressing - as if meaningful 
dialogues were commonplace on this planet. Philip Morrison, of the Massachusetts 
Institute of Technology, has pointed out that such cultural monologues are 
entirely common in the history of mankind; that, for example, the entire cultural 
patrimony of classical Greece, which has influenced our civilization in a profound 
way, has traveled in only one direction in time. We have not sent our wisdom to 
the Greeks. The Greeks have sent their wisdom to us - on paper and parchment, 
and not by radio waves, but the principle is the same. 

The scientific, logical, cultural, and ethical knowledge to be gained by tuning 
into galactic transmissions may be, in the long run, the most profound single event 
in the history of our civilization. There will be information in what we will no 
longer be able to call the humanities - because our communicants will not be 
human. There will be a deparochialization of the way we view the cosmos and 
ourselves. There will be a new perspective on the differences we perceive among 
ourselves once we grasp the enormous differences that will exist between us and 
beings elsewhere - beings with whom we have nonetheless a serious commonality 
of intellectual interest. 

But, at the same time, it is not likely to result in discontinuous change. The 
information may flutter one day into our radio telescopes at a breathtaking rate of 
information transfer. The decoding of the message, the understanding of the 
contents, and the extremely cautious application of what we are taught might take 
decades or even centuries. 

The cultural shock from the content of the message is likely, in the short run, 
to be small. The main impact will be the receipt of the message itself. Landing of 
men on the Moon is now considered, at least in the United States, as such a 
commonplace and relatively uninteresting occurrence that I think we can say the 
receipt of a message from an extraterrestrial civilization, a message that will take a 
long time to decode and understand, will not be very much more disorienting to 
the average man. 

Eventually, we may wish to respond. 

Why should an advanced society wish to expend the effort to communicate 
such information to a backward, emerging, novice civilization like our own? I can 
imagine that they are motivated by benevolence; that during their emerging 
phases, they were themselves helped along by such messages and that this is a 
tradition worthy of continuance. There are some science-fiction stories in which 
the contents of the message are malevolent, in which we receive instructions for 


the construction of a machine, which we then dutifully build and it then dutifully 
takes over the Earth. But no one will blindly construct such a machine. No one 
will implement the instructions contained in an extraterrestrial message until the 
full theoretical underpinnings and scientific bases of the instructions are well 
understood. This is one reason why the short-term cultural shock of a message will 
be small. I do not believe that there is any significant danger from the receipt of 
such a message, provided the most elementary cautions are adhered to. 

It has been suggested that the contents of the initial message received will 
contain instructions for avoiding our own self-destruction, a possibly common fate 
of societies shortly after they reach the technical phase. There are certainly enough 
nuclear weapons on our planet today to destroy every man, woman, and child 
many times over. It is proposed that advanced extraterrestrial civilizations, 
motivated either by altruism or through a selfish interest in maintaining a 
stimulating set of communicants, convey the information for stabilizing societies. I 
do not know if this is possible; historical differences between organisms and 
societies with billions of years of independent evolution would be enormous. But 
it is a possibility not worth ignoring, this feedback hypothesis that the existence of 
interstellar communication enlarges the number of civilizations and may be the 
agency of our own survival. There is another way in which such a feedback 
process works, even if there are no specific instructions on how to avoid 
destroying ourselves. There is the matter of time scale. Governments on Earth 
rarely plan more than five years into the future. Individuals ordinarily make 
detailed plans for only much shorter times. Even an unsuccessful search for 
extraterrestrial intelligence, which may take decades or centuries, is a useful 
example of long-range planning. But think of the consequences of receiving a 
message that was transmitted three hundred years ago, and a discussion of which 
will take another six hundred years. Awaiting the answer to our reply requires a 
continuity of purpose unusual in human institutions. Much of the current 
ecological catastrophe is due to a grasp of short-term gains and an awesome 
blindness to long-term disasters. The time scale of interstellar civilizations and 
discourse with them provides a sense of historical continuity vital for the 
continuance of our own civilization. 


31. Cables, Drums, and Seashells 

In almost all scientific descriptions of contact between Earth and an 
extraterrestrial civilization, the extraterrestrial civilization is described as 

Why advanced? Why aren't there any primitive civilizations out there, 
backward fellows poking around, fumbling over interstellar debris, constantly 
botching things up? Why are we obsessed with advanced civilizations? 

The answer is very simple: The primitive ones don't talk to us. (The really 
smart ones may not talk to us, either, but that is a point I'll come to in a moment.) 

Let us consider contact using radio astronomy. Radio astronomy on Earth is a 
by-product of the Second World War, when there were strong military pressures 
for the development of radar. Serious radio astronomy emerged only in the 1950s, 
major radio telescopes only in the 1960s. If we define an advanced civilization as 
one able to engage in long-distance radio communication using large radio 
telescopes, there has been an advanced civilization on our planet for only about 
ten years. Therefore, any civilization ten years less advanced than we cannot talk 
to us at all. 

Even rather optimistic estimates of the rate at which advanced technical 
civilizations emerge in the Galaxy are lower than one every ten years (see Chapter 
28). If this is correct, it means that of all the civilizations in the Galaxy able to 
communicate by radio, there is none as dumb as we. There may be millions of 
civilizations less advanced than we, but we have no way to make contact with 
them: They lack the technology to receive or transmit. Objections that the Pioneer 
10 message may be too difficult for the recipients to decipher ignores the fact that 
the recipients must be able to acquire this tiny bit of space debris in interstellar 
space - a task vastly beyond our present capabilities. If they are advanced enough 
to capture Pioneer 10 in the dark between the stars, they will, I think, be smart 
enough to make out its message, which can be read without special hinting by 
many physicists on as backward a planet as Earth (although, to be sure, those 
physicists share some genetic and cultural biases and chauvinisms with the authors 
of the message). 

But what about civilizations vastly in advance of our own? The amount of 
technical progress we have made in the past few hundred years is startling. Not 
only have entire new technologies developed, but entire new laws of physics and 
entire new ways of examining the universe have evolved. This intellectual and 
technological development is continuing. If Earth's civilization survives, the 
advance of science and technology will also continue. 

Civilizations hundreds or thousands or millions of years beyond us should have 
sciences and technologies so far beyond our present capabilities as to be 
indistinguishable from magic. It is not that what they can do violates the laws of 
physics; it is that we will not understand how they are able to use the laws of 
physics to do what they do. 


It is possible that we are so backward and so uninteresting to such civilizations 
as not to be worthy of contact, or at least of much contact. There may be a few 
specialists in primitive planetary societies who receive master's or doctor's degrees 
in studying Earth or listening to our raspy radio and television traffic. There may 
be amateurs - Boy Scouts, radio hams, and the equivalent — who may be interested 
in developments on Earth. But a civilization a million years in our future is 
unlikely, I believe, to be very interested in us. There are all those other 
civilizations a million years in our future for them to talk to. 

Communications between two very advanced civilizations will likely use a 
science and a technology inaccessible to us. We therefore have no prospect for 
tuning in on such communications traffic, either accidentally or on purpose. 

We are like the inhabitants of an isolated valley in New Guinea who 
communicate with societies in neighboring valleys (quite different societies, I 
might add) by runner and by drum. When asked how a very advanced society will 
communicate, they might guess by an extremely rapid runner or by an improbably 
large drum. They might not guess a technology beyond their ken. And yet, all the 
while, a vast international cable and radio traffic passes over them, around them, 
and through them. 

At this very moment the messages from another civilization may be wafting 
across space, driven by unimaginably advanced devices, there for us to detect them 
- if only we knew how. Perhaps the message will come via radio waves to be 
detected by large radio telescopes. Or perhaps by more arcane devices, the 
modulation of X-ray stars, gravity waves, neutrinos, tachyons, or transmission 
channels that no one on Earth will dream of for centuries. Or perhaps the 
messages are already here, present in some everyday experience that we have not 
made the right mental effort to recognize. The power of such an advanced 
civilization is very great. Their messages may lie in quite familiar circumstances. 

Consider, for example, seashells. Everyone knows the "sound of the sea" to be 
heard when putting a seashell to one's ear. It is really the greatly amplified sound 
of our own blood rushing, we are told. But is this really true? Has this been 
studied? Has anyone attempted to decode the message being sounded by the 
seashell? I do not intend this example as literally true, but rather as an allegory. 
Somewhere on Earth there may be the equivalent of the seashell communications 
channel. The message from the stars may be here already. But where? 

We will listen for the interstellar drums, but we will miss the interstellar 
cables. We are likely to receive our first messages from the drummers of the 
neighboring galactic valleys - from civilizations only somewhat in our future. The 
civilizations vastly more advanced than we will be, for a long time, remote both in 
distance and accessibility. At a future time of vigorous interstellar radio traffic, the 
very advanced civilizations may be, for us, still insubstantial legends. 


The night freight to the star*. By Jon Lombcrg. 


32. The Night Freight to the Stars 

For three generations of human beings there was - as an ever-present, but almost 
unperceived, part of their lives - a sound that beckoned, a call that pierced the 
night, carrying the news that there was a way, not so very difficult, to leave Twin 
Forks, North Dakota, or Apalachicola, Florida, or Brooklyn, New York. It was the 
wail of the night freight, as haunting and evocative as the cry of the loon. It was a 
constant reminder that there were vehicles, devices, which, if boarded, could 
propel you at high velocity out of your little world into a vaster universe of forests 
and deserts, seacoasts and cities. 

Especially in the United States, but perhaps over much of the world, few 
people today travel by train. There are whole generations growing up which have 
never heard that siren call. This is the moment of the homogenization of the 
world, when the diversities of societies are eroding, when a global civilization is 
emerging. There are no exotic places left on Earth to dream about. 

And for this reason there remains an even greater and more poignant need 
today for a vehicle, a device, to get us somewhere else. Not all of us; only a few - 
to the deserts of the Moon, the ancient seacoasts of Mars, the forests of the sky. 
There is something comforting in the idea that one day a few representatives of 
our little terrestrial village might venture to the great galactic cities. 

There are as yet no interstellar trains, no machines to get us to the stars. But 
one day they may be here. We will have constructed them or we will have 
attracted them. 

And then there will once again be the whistle of the night freight. Not the 
antique sort of whistle, for sound does not carry in interplanetary space or in the 
emptiness between the stars. But there will be something, perhaps the flash from 
magnetobrehmstrahlung, as the starship approaches the velocity of light. There 
will be a sign. 

Looking out on a clear night from the continent-sized cities and vast game 
preserves that may be our future on this planet, youngsters will dream that when 
they are grown, if they are very lucky, they will catch the night freight to the stars. 


33- Astroengineering 

In a by now much quoted and possibly even apocryphal story, the nuclear 
physicist Enrico Fermi asked, during a luncheon conversation at Los Alamos in the 
middle 1940s, "Where are they?" If there are vast numbers of beings more 
advanced then we, he was musing, why have we seen no sign of them - by a 
visitation to Earth, for example? 

We have discussed this problem in Chapters 27 and 28. But there is another 
formulation of Fermi's question. A civilization a hundred years in our 
technological future (assuming present rates of technological growth) would surely 
be able to communicate by radio, and possibly by other techniques, anywhere in 
the Galaxy and probably with other galaxies as well. A civilization thousands of 
years in our technological future will very likely be able to travel physically 
between the stars, although with the expenditure of considerable time and 

But what of civilizations tens of thousands or hundreds of thousands of years in 
our future, or even farther advanced? There are, after all, stars billions of years 
older than the Sun. The very oldest such stars lack heavy metals; probably their 
planets are similarly lacking. Such very old stars are inhospitable environments for 
the development of technological civilizations. But some stars one or two billion 
years older than the Sun have no such attendant difficulties. It is surely possible 
that there are at least a few civilizations hundreds of millions or billions of years in 
our technological future. 

With prodigious energy resources, such civilizations should be able to rework 
the cosmos. We have discussed in Chapter 22 how life on Earth has already altered 
our planet significantly and how we can envision in the relatively near future 
making important changes in the environments of the nearby planets. 

More major changes are possible in the somewhat more distant future. The 
mathematician Freeman Dyson, of the Institute for Advanced Study, offers a 
scheme in which the planet Jupiter is broken down piece by piece, transported to 
the distance of the Earth from the Sun, and reconstructed into a spherical shell — a 
swarm of individual fragments revolving about the Sun. The advantage of Dyson's 
proposal is that all of the sunlight now wasted by not falling upon an inhabited 
planet could then be gainfully employed; and a population greatly in excess of that 
which now inhabits the Earth could be maintained. Whether such a vast 
population is desirable is an important and unsolved question. But what seems 
clear is that at the present rate of technological progress it will be possible to 
construct such a Dyson sphere in perhaps some thousands of years. In that case, 
other civilizations older than we may have already constructed such spherical 

A Dyson sphere absorbs visible light from the Sun. But it does not continue 
indefinitely to absorb this light without re-radiating; otherwise, the temperature 
would become impossibly high. The exterior of the Dyson sphere radiates infrared 


radiation into space. Because of the large dimensions of the sphere, the infrared 
flux from a Dyson sphere should be detectable over quite sizable distances - with 
present infrared technology, over distances of hundreds to thousands of light-years. 
Remarkably enough, large infrared objects of roughly Solar System dimensions and 
of temperatures less than 1,000 degrees Fahrenheit have been detected in recent 
years. These, of course, are not necessarily Dyson civilizations. They may be vast 
dust clouds surrounding stars in the process of formation. But we are beginning to 
detect objects that are not dissimilar to the artifacts of advanced civilizations. 

There are many phenomena in contemporary astronomy that are not 
understood. Quasars, for example, are one. The reported very high- intensity 
gravitational waves coming from the center of our galaxy are another. The list can 
be extended considerably. As long as we do not understand these phenomena, we 
cannot exclude the possibility that they are manifestations of extraterrestrial 
intelligence. This hardly demonstrates the likelihood of extraterrestrial 
intelligence, any more than our inability to understand seasonal changes on Mars 
(Chapter 19) provided strong evidence for vegetation on that planet. As the Soviet 
astrophysicist I. S. Shklovskii says, "Following the principles of law, we should 
assume all astronomical phenomena natural until proven otherwise." 

Some scientists have asked, in the reformulation of Fermi's question, why it is 
that advanced civilizations are not much more obvious. Why have stars not been 
rearranged into entirely artificial patterns in the sky - perhaps blinking advertising 
lights, detectable over intergalactic distances, for some cosmic soft drink? This 
particular example is, of course, not very tenable - one society's soft drink may be 
another society's poison. More seriously, the manifestations of very advanced 
civilizations may not be in the least apparent to a society as backward as we, any 
more than an ant performing his anty labors by the side of a suburban swimming 
pool has a profound sense of the presence of a superior technical civilization all 
around him. 


Type MM Civilization by Jon Lemberg 

34- Twenty Questions: A Classification of Cosmic 


To deal with the possibility of enormously advanced extraterrestrial civilizations, 
the Soviet astrophysicist N. S. Kardashev has proposed a distinction in terms of the 
energy available to a civilization for communications purposes. 

A Type I civilization is able to muster for communications purposes the 
equivalent of the entire present power output of the planet Earth - which is now 
used for heating, electricity, transportation, and so on; a large variety of purposes 
other than communication with extraterrestrial civilizations. By this definition the 
Earth is not yet a Type I civilization. 

The power usage of our civilization is growing at a rapid rate. The present 
power output of planet Earth is something like 10 15 or 10 16 watts; that is, a million 
billion to ten million billion watts. The standard exponential notation simply 
indicates the number of zeros following the 1. For example, 10 15 means fifteen 
zeros after the 1. The concept of power in physics is that of an energy expenditure 
per unit time. One watt is ten million ergs of energy expended per second. All of 
the power used on the Earth is thus equivalent to lighting up, say, one hundred 
trillion hundred-watt bulbs. Especially if this energy were put out in the radio part 
of the spectrum, it might be detected over very sizable distances. 

A Type II civilization is able to use for communications purposes a power 
output equivalent to that of a typical star, about 10 26 watts. We already see 
particularly bright stars at optical frequencies in the nearest galaxies. A Type II 
civilization, putting out in our direction 10 26 watts in some fairly narrow radio 
bandpass, could be detectable over vast inter-galactic distances. It would be easily 
detectable, if we used the right search procedures, were there only one such 
civilization in the nearest spiral galaxy to our own, M31, the great galaxy in the 
constellation Andromeda. M31 is by no means the largest galaxy. For example, an 
elliptical galaxy, M87 — also known as Virgo A - contains perhaps 10 trillion stars. 

Finally, Kardashev imagines a Type III civilization, which would use for 
communications purposes the energy output of an entire galaxy, roughly 10 36 
watts. A Type III civilization beaming at us could be detected if it were anywhere 
in the universe. There is no provision for a Type IV civilization, which by 
definition talks only to itself. There need not be many Type II or Type III 
civilizations for their presence to be felt once a search for extraterrestrial 
civilizations is organized in earnest. It may well be that a few Type II or Type III 
civilizations would be far more readily detectable than a large number of Type I 
civilizations - if they choose to signal us (see Chapter 31). 

The energy gap between a Type I and a Type II civilization or between a Type 
II and a Type III civilization is enormous - a factor of about ten billion in each 
instance. It seems useful, if the matter is to be considered seriously, to have a finer 
degree of discrimination. I would suggest Type 1.0 as a civilization using ro l6 watts 


for interstellar communication; Type 1.1, 10 17 watts; Type 1.2, 10 18 watts, and so 
on. Our present civilization would be classed as something like Type 0.7. 

But there may be more significant ways to characterize civilizations than by the 
energy they use for communications purposes. An important criterion of a 
civilization is the total amount of information that it stores. This information can 
be described in terms of bits, the number of yes-no statements concerning itself 
and the universe that such a civilization knows. 

An example of this concept is the popular game of "Twenty Questions," as 
played on Earth. One player imagines an object or concept and makes an initial 
classification of it into animal, vegetable, mineral, or none of these three. To 
identify the object or concept, the other players then have a total of twenty 
questions, which can only be answered "Yes" or "No." How much information can 
be discriminated in this manner? 

The initial characterization can be thought of as three yes-no questions: 
Conceptual or objective? Biological or nonbiological? Plant or animal? If we agree 
that a particular game of "Twenty Questions" is in pursuit of something alive, we 
have, in effect, answered three questions already by the time the game begins. The 
first question divided the universe into two (unequal) pieces. The second question 
divided one of those pieces into two more, and the third divided one of those 
pieces into yet two more. At this stage we have divided the universe crudely into 
2X2X2— 2 3 — 8 pieces. When we have finished with our twenty questions, we have 
"divided the universe into 2 10 additional (probably unequal) pieces. Now, 2 10 is 
1,024. We can perform such calculations fairly quickly if we approximate 2 10 by 
i,ooo=io 3 ; therefore, 2 20 equals (2 10 ) 2 , which approximately equals (io 3 ) 2 =io 6 . The 
total number of effective questions, twenty-three, has divided the universe into 
about 2 23 , or approximately 10 7 pieces or bits. Thus, it is possible for skillful 
players to win at "Twenty Questions" only if they live in a civilization that has an 
information content of about 10 7 bits. 

But, as I discuss below, our civilization is characterized by perhaps 10 14 bits. 
Therefore, skillful players should win at "Twenty Questions" only about 10 7 out of 
10 14 times, or one in 10 7 , or one in ten million times. That the game is won more 
often in practice is because there is an additional rule — usually unstated but well 
understood: Namely, that the object or concept being named should be one in the 
general cultural heritage of all the players. But this must mean that 10 7 bits can 
convey a great deal of information about a civilization, as indeed it can. Philip 
Morrison has estimated that the total written contribution to our present 
civilization from classical Greek civilization is only about 10 9 bits. Thus, a one-way 
message, containing what, by the standards of modern radio astronomy, is a very 
small number of bits, can contain a very significant amount of new information 
and can have a powerful influence on a society in the long run. 

What is the total number of bits in an English word? In all the books in the 
world? There are in general English usage twenty-six letters and a sprinkling of 
punctuation marks. Let us estimate that there are thirty-two such effective 


"letters." But 32 =2 5 ; that is, there are something like five bits per letter. If a typical 
word has four to six letters (for an average of six letters a word, there would have 
to be a lot of fancy words), there will then be about twenty to thirty bits per 
word. A typical book - about three hundred words per page and about three 
hundred pages - would have about a hundred thousand words, or about three 
million bits. The largest libraries in the world, such as the British Museum, the 
Bodleian Library at Oxford, the New York Public Library, the Widener Library at 
Harvard, and the Lenin Library in Moscow, have no more than about ten million 
volumes. This is about 3Xio 13 bits. 

A poor-quality low-resolution photograph may have a million bits in it. A 
quite complex caricature or cartoon might have only about a thousand bits. On 
the other hand, a large, high-quality color photograph or painting might have 
about a billion bits. Let us make allowances for the amount of fundamental 
information contained in graphics, photography, and art in our civilization, as well 
as the recorded oral tradition. Let us also try to estimate - this can be done only 
very crudely — the information we are born with about how to deal with the 
world. (Human beings are, relative to other animals, born with very little such 
information - we deal with the world much more in terms of learned rather than 
inherited or instinctual information.) I estimate, then, that we and our civilization 
can be very well characterized by something like 10 14 or 10 15 bits. 

Parenthetically, the ancient Chinese saying that a single picture is worth ten 
thousand words (three hundred thousand bits in English; but in Chinese?) is 
approximately correct - provided that the picture is not too complex. 

We can imagine civilizations that have a much greater number of bits 
characterizing their society than characterizes ours. In general, we would expect a 
civilization high on the energy scale to be high on the information scale. But this 
need not necessarily be true. I certainly can imagine societies that are very 
complex and require many more bits to characterize them than our society 
requires - but that are not interested in interstellar communication. 
Characterization of interstellar civilizations requires us to characterize their 
information content as well. 

If we have used numbers to describe energy, we should perhaps use letters to 
describe information. There are twenty-six letters in the English alphabet. If each 
corresponds to a factor of ten in the number of bits, there is the possibility of 
characterizing with the English alphabet a range of information contents over a 
factor of 10 26 - a very large range, which seems adequate for our purposes. I 
propose calling a Type A civilization one at the "Twenty Questions" level, 
characterized by 10 6 bits. In practice this is an extremely primitive society - more 
primitive than any human society that we know well - and a good beginning 
point. The amount of information we have acquired from Greek civilization 
would characterize that civilization as Type C, although the actual amount of 
information that characterized Periclean Athens is probably equivalent to Type E 

or so. By these standards, our contemporary civilization, if characterized by 10 14 
bits of information, corresponds to a Type H civilization. 

A combined energy/ information characterization of our present global 
terrestrial society is Type 0.7H. First contact with an extraterrestrial civilization 
would be, I would guess, with a type such as 1.5J or 1.8K. If there were a galactic 
civilization of a million worlds, and if each were characterized by a thousand times 
the information content of our terrestrial civilization, that galactic civilization 
would be of Type Q. A billion such federated galaxies, with all the information 
held collectively, would be characterized as a civilization of Type Z. 

But as we argue in the next chapter, there is not enough time in the history of 
the cosmos for such an intergalactic society to have developed. The run of letters 
from A to Z appears to run the gamut from societies much more primitive than 
any of Man's to societies more advanced than any that could be. 


Symbol of a unified galaxy by Jon Lombcrg. The galaxy 
psunted is M7*4 in the ctmstcllatiafi Pisces. 

35- Galactic Cultural Exchanges 

It is possible to speculate on the very distant future of advanced civilizations. We 
can imagine such societies in excellent harmony with their environments, their 
biology, and the vagaries of their politics, so that they enjoy extraordinarily long 
lifetimes. Communications would long have been established with many other 
such civilizations. The diffusion of knowledge, techniques, and points of view 
would occur at the velocity of light. In time, the diverse cultures of the Galaxy, 
involving a large number of quite different-looking organisms, based on different 
biochemistries and different initial cultures, would become homogenized - just as 
the diverse cultures of Earth today are in the process of homogenization. 

But such cultural homogenization of the Galaxy will take a long time. One 
round-trip communication by radio between us and the center of the Milky Way 
Galaxy requires sixty thousand years. Cultural homogenization of the Galaxy 
would require many such exchanges, even if each exchange involved very large 
amounts of information conveyed very efficiently. I find it difficult to believe that 
fewer than one hundred exchanges between the remotest parts of the Galaxy 
would be adequate for galactic cultural homogenization. 

The minimum lifetime for the homogenization of the Galaxy would thus be 
many millions of years. The constituent societies must, of course, be stable for 
comparable periods of time. Such homogenization need not be desirable, but there 
are still strong and obvious pressures for it to occur, as is also the case on the 
Earth. If there exists a galactic community of civilizations that truly embraces 
much of the Milky Way, and if we are right that no information can be 
transmitted at a velocity faster than light, then most of the members - and all of 
the founding members - of such a community must be at least millions of years 
more advanced than we are. For this reason, I think it a great conceit, the idea of 
the present Earth establishing radio contact and becoming a member of a galactic 
federation - something like a bluejay or an armadillo applying to the United 
Nations for member- nation status. 

These velocity-of-light limitations on the speed of communication can also be 
applied to the homogenization of the cultures of different galaxies, after a 
hypothetical period of millions of years in which the stellar civilizations of a given 
galaxy achieve a common culture. W e can imagine attempts to make contact with 
such galactic federations in other galaxies. 

The nearest spiral galaxies are several million light-years away. This means that 
a single element of the dialogue - a message and its reply — would take periods of 
time of several millions to about ten million years. If a hundred such exchanges are 
required, the time scale for homogenization of a group of nearby galaxies is then of 
the order of a billion years. The galactic societies would have to be stable and 
preserve continuity for such periods of time. This would mean that an immensely 
old civilization within our Galaxy might have strong learned commonalities with 


similar galactic federations in other members of what astronomers modestly call 
the "local" group of galaxies. 

These homogenization time scales are beginning to reach a point that strains 
credulity. There are sufficient natural catastrophes and statistical fluctuations in 
the universe that a stable society - even residing on many different planets 
simultaneously for more than a billion years - begins to sound unlikely. Also, 
during these immense periods of time the communicating galactic societies will 
themselves be evolving; many contacts will be required to maintain 
homogenization. The galaxies are so distant one from another that they will always 
retain their cultural individuality. 

In any case, all bets are off beyond the local group. To have cultural 
homogenization with the next such cluster of galaxies like our own, and engage in 
a hundred message-exchange pairs, would require a time longer than the age of the 
universe. This is not to exclude long individual messages from one galaxy to 
another. It may be that enormous amounts of information - about the history of a 
given galactic federation, for example - may be well known to civilizations in 
other galaxies. But there will not be enough time for dialogues. At most, one 
exchange would be possible between the most distant galaxies in the universe. 
Two exchanges of information at the velocity of light would take more time than 
there is, according to modern cosmology. 

We conclude that there cannot be a strongly cohesive network of 
communicating, unifying intelligences through the whole universe if (1) such 
galactic civilizations evolve upward from individual planetary societies and if (2) 
the velocity of light is indeed a fixed limit on the speed of information 
transmission, as special relativity requires (i.e., if we ignore such possibilities as 
using black holes for fast transport: See Chapter 39). Such a universal intelligence 
is a kind of god that cannot exist. 

In a way, St. Augustine and many other thoughtful theologians have come to 
rather the same conclusion - God must not live from moment to moment, but 
during all times simultaneously. This is, in a way, the same as saying that special 
relativity does not apply to Him. But supercivilization gods, perhaps the only ones 
that this kind of scientific speculation admits, are fundamentally limited. There 
may be such gods of galaxies, but not of the universe as a whole. 


Illustration after H. C. Wells’ The Time Machine. From 

Classics Illustrated. 


36. A Passage to Elsewhen 

One of the most pervasive and entrancing ideas of science fiction is time travel. In 
The Time Machine, the classic story by H. G. Wells, and in most subsequent 
renditions, there is a small machine, constructed usually by a solitary scientist in a 
remote laboratory. One dials the year of interest, steps into the machine, presses a 
button, and presto, here's the past or the future. Among the common devices in 
time-travel stories are the logical paradoxes that accompany meeting yourself 
several years ago; killing a lineal antecedent; interfering directly with a major 
historical event of the past few thousand years; or accidentally stepping on a 
Precambrian butterfly — you are always changing the entire subsequent history of 

Such logical paradoxes do not occur in stories about travel to the future. 
Except for the element of nostalgia - the wish we all have to relive or reclaim 
some elements of the past - a trip forward in time is surely at least as exciting as 
one backward in time. We know rather much about the past and almost nothing 
about the future. Travel forward in time has a greater degree of intellectual 
excitement than the reverse. 

There is no question that time travel into the future is possible: We do it all 
the time merely by aging at the usual rate. But there are other, more interesting 
possibilities. Everyone has heard about, and now even a fair number of people 
understand, Einstein's special theory of relativity. It was Einstein's genius to have 
subjected our usual views of space, time, and simultaneity to a penetrating logical 
analysis, which could have been performed two centuries earlier. But special 
relativity required for its discovery a mind divested of the conventional prejudices 
and the blind adherence to prevailing beliefs - a rare mind in any time. 

Some of the consequences of special relativity are counterintuitive, in the sense 
that they do not correspond to what everybody knows by observing his 
surroundings. For example, the special theory says that a measuring rod shrinks in 
the direction in which it is moving. When jogging, you are thinner in the direction 
in which you are jogging — and not because of any weight loss. The moment you 
come to a halt you immediately resume your usual paunch-to-backbone 
dimension. Similarly, we are more massive when running than when standing still. 
These statements appear silly only because the magnitude of the effect is too small 
to be measured at jog velocities. But were we able to jog at some close 
approximation to the speed of light (186,000 miles per second), these effects 
would become manifest. In fact, expensive synchrotrons - machines to accelerate 
charged particles close to the speed of light - take account of such effects, and 
work only because special relativity happens to be correct. The reason these 
consequences of special relativity seem counterintuitive is that we are not in the 
habit of traveling close to the speed of light. It is not that there is anything wrong 
with common sense; common sense is fine in its place. 

There is a third consequence of special relativity, a bizarre effect important 
only close to the speed of light: The phenomenon called time dilation. Were we to 
travel close to the speed of light, time, as measured by our wristwatch or by our 
heartbeat, would pass more slowly than a comparable but stationary clock. Again, 
this is not an experience of our everyday life, but it is an experience of nuclear 
particles, which have clocks built into them (their decay times) when they travel 
close to the speed of light. Time dilation is a measured and authenticated reality of 
the universe in which we live. 

Time dilation implies the possibility of time travel into the future. A space 
vehicle that could travel arbitrarily close to the speed of light arranges for time, as 
measured on the space vehicle, to move as slowly as desired. For example, our 
Galaxy is some sixty thousand light-years in diameter. At the velocity of light, it 
would take sixty thousand years to cross from one end of the Galaxy to the other. 
But this time is measured by a stationary observer. A space vehicle able to move 
close to the speed of light could traverse the Galaxy from one end to the other in 
less than a human lifetime. W ith the appropriate vehicle we could circumnavigate 
the Galaxy and return almost two hundred thousand years later, as measured on 
Earth. Naturally, our friends and relatives would have changed some in the interval 
- as would our society and probably even our planet. 

According to special relativity, it is even possible to circumnavigate the entire 
universe within a human lifetime, returning to our planet many billions of years in 
our future. According to special relativity, there is no prospect of traveling at the 
speed of light, merely very close to it. And there is no possibility in this way of 
traveling backward in time; we can merely make time slow down, we cannot 
make it stop or reverse. 

The engineering problems involved in the design of space vehicles capable of 
such velocities are immense. Pioneer io, the fastest man-made object ever to leave 
the Solar System, is traveling about ten thousand times slower than the speed of 
light. Time travel into the future is thus not an immediate prospect, but it is a 
prospect conceivable for an advanced technology on planets of other stars. 

There is one further possibility that should be mentioned; it is a much more 
speculative prospect. At the end of their lifetimes, stars more than about 2.5 times 
as massive as our Sun undergo a collapse so powerful that no known forces can 
stop it. The stars develop a pucker in the fabric of space — a "black hole" - into 
which they disappear. The physics of black holes does not involve Einstein's 
special theory of relativity; it involves his much more difficult general theory of 
relativity. The physics of black holes - particularly, rotating black holes - is rather 
poorly understood at the present time. There is, however, one conjecture that has 
been made, which cannot be disproved and which is worthy of note: Black holes 
may be apertures to elsewhen. Were we to plunge down a black hole, we would 
re-emerge, it is conjectured, in a different part of the universe and in another 
epoch in time. We do not know whether it is possible to get to this other place in 
the universe faster down a black hole than by the more usual route. We do not 


know whether it is possible to travel into the past by plunging down a black hole. 
The paradoxes that this latter possibility imply could be used to argue against it, 
but we really do not know. 

For all we do know, black holes are the transportation conduits of advanced 
technological civilizations - conceivably, conduits in time as well as in space. A 
large number of stars are more than 2.5 times as massive as the Sun; as far as we 
can tell, they must all become black holes during their relatively rapid evolution. 

Black holes may be entrances to Wonderlands. But are there Alices or white 

The Triffid nebula, a dense cloud of dust and gas out of 
which bright stars are forming. Courtesy, Steward Observa- 
tory. University of Arizona. 


37- Starfolk 

I.A Fable 

Once upon a time, about ten or fifteen billion years ago, the universe was 
without form. There were no galaxies. There were no stars. There were no 
planets. And there was no life. Darkness was upon the face of the deep. The 
universe was hydrogen and helium. The explosion of the Big Bang had passed, and 
the fires of that titanic event - either the creation of the universe or the ashes of a 
previous incarnation of the universe - were rumbling feebly down the corridors of 

But the gas of hydrogen and helium was not smoothly distributed. Here and 
there in the great dark, by accident, somewhat more than the ordinary amount of 
gas was collected. Such clumps grew imperceptibly at the expense of their 
surroundings, gravitationally attracting larger and larger amounts of neighboring 
gas. As such clumps grew in mass, their denser parts, governed by the inexorable 
laws of gravitation and conservation of angular momentum, contracted and 
compacted, spinning faster and faster. Within these great rotating balls and 
pinwheels of gas, smaller fragments of greater density condensed out; these 
shattered into billions of smaller shrinking gas balls. 

Compaction led to violent collisions of the atoms at the centers of the gas balls. 
The temperatures became so great that electrons were stripped from protons in 
the constituent hydrogen atoms. Because protons have like positive charges, they 
ordinarily electrically repel one another. But after a while the temperatures at the 
centers of the gas balls became so great that the protons collided with 
extraordinary energy - an energy so great that the barrier of electrical repulsion 
that surrounds the proton was penetrated. Once penetration occurred, nuclear 
forces - the forces that hold the nuclei of atoms together - came into play. From 
the simple hydrogen gas the next atom in complexity, helium, was formed. In the 
synthesis of one helium atom from four hydrogen atoms there is a small amount of 
excess energy left over. This energy, trickling out through the gas ball, reached the 
surface and was radiated into space. The gas ball had turned on. The first star was 
formed. There was light on the face of the heavens. 

The stars evolved over billions of years, slowly turning hydrogen into helium in 
their deep interiors, converting the slight mass difference into energy, and flooding 
the skies with light. There were in these times no planets to receive the light, and 
no life forms to admire the radiance of the heavens. 

The conversion of hydrogen into helium could not continue indefinitely. 
Eventually, in the hot interiors of the stars, where the temperatures were high 
enough to overcome the forces of electrical repulsion, all the hydrogen was 
consumed. The fires of the stars were stoked. The pressures in the interiors could 
no longer support the immense weight of the overlying layers of star. The stars 


then continued their process of collapse, which had been interrupted by the 
nuclear fires of a billion years before. 

In contracting further, higher temperatures were reached, temperatures so high 
that helium atoms - the ash of the previous epoch of nuclear reaction - became 
usable as stellar fuel. More complex nuclear reactions occurred in the insides of 
the stars - now swollen, distended red giant stars. Helium was converted to 
carbon, carbon to oxygen and magnesium, oxygen to neon, magnesium to silicon, 
silicon to sulfur, and upward through the litany of the periodic table of the 
elements - a massive stellar alchemy. V ast and intricate mazes of nuclear reactions 
built up some nuclei. Others coalesced to form much more complex nuclei. Still 
others fragmented or combined with protons to build only slightly more complex 

But the gravity on the surfaces of red giants is low, because the surfaces have 
expanded outward from the interiors. The outer layers of red giants are slowly 
dissipated into interstellar space, enriching the space between the stars in carbon 
and oxygen and magnesium and iron and all the elements heavier than hydrogen 
and helium. In some cases, the outer layers of the star were slowly stripped off, 
like the successive skins of an onion. In other cases, a colossal nuclear explosion 
rocked the star, propelling at immense velocity into interstellar space most of the 
outside of the star. Either by leakage or explosion, by dissipation slow or 
dissipation fast, star-stuff was spewed back to the dark, thin gas from which the 
stars had come. 

But here, later generations of stars were aborning. Again the condensations of 
gas spun their slow gravitational pirouettes, slowly transmogrifying gas cloud into 
star. But these new second- and third-generation stars were enriched in heavy 
elements, the patrimony of their stellar antecedents. Now, as stars were formed, 
smaller condensations formed near them, condensations far too small to produce 
nuclear fires and become stars. They were little dense, cold clots of matter, slowly 
forming out of the rotating cloud, later to be illuminated by the nuclear fires that 
they themselves could not generate. These unprepossessing clots became the 
planets: Some giant and gaseous, composed mostly of hydrogen and helium, cold 
and far from their parent star; others, smaller and warmer, losing the bulk of their 
hydrogen and helium by a slow trickling away to space, formed a different sort of 
planet - rocky, metallic, hard-surfaced. 

These smaller cosmic debris, congealing and warming, released small quantities 
of hydrogen-rich gases, trapped in their interiors during the processes of formation. 
Some gases condensed on the surface, forming the first oceans; other gases 
remained above the surface, forming the first atmospheres - atmospheres different 
from the present atmosphere of Earth, atmospheres composed of methane, 
ammonia, hydrogen sulfide, water, and hydrogen - an unpleasant and un- 
breathable atmosphere for humans. But this is not yet a story about humans. 

Starlight fell on this atmosphere. Storms were driven by the Sun, producing 
thunder and lightning. Volcanoes erupted, hot lava heating the atmosphere near 


the surface. These processes broke apart molecules of the primitive atmosphere. 
But the fragments reassorted into more and more complex molecules, falling into 
the early oceans, there interacting with each other, falling by chance upon clays, a 
dizzying process of breakdown, resynthesis, transformation - slowly moving 
toward molecules of greater and greater complexity, driven by the laws of physics 
and chemistry. After a time, the oceans achieved the constituency of a warm 
dilute broth. 

Among the innumerable species of complex organic molecules forming and 
dissipating in this broth there one day arose a molecule able crudely to make 
copies of itself - a molecule which weakly guided the chemical processes in its 
vicinity to produce molecules like itself - a template molecule, a blueprint 
molecule, a self-replicating molecule. This molecule was not very efficient. Its 
copies were inexact. But soon it gained a significant advantage over the other 
molecules in the early waters. The molecules that could not copy themselves did 
not. Those that could, did. The number of copying molecules greatly increased. 

As time passed, the copying process became more exact. Other molecules in 
the waters were reprocessed to form the jigsaw puzzle pieces to fit the copying 
molecules. A minute and imperceptible statistical advantage of the molecules that 
could copy themselves was soon transformed by the arithmetic of geometrical 
progression into the dominant process in the oceans. 

More and more elaborate reproductive systems arose. Those systems that 
copied better produced more copies. Those that copied poorly produced fewer 
copies. Soon most of the molecules were organized into molecular collectives, into 
self-replicating systems. It was not that any molecules had the glimmering of an 
idea or the ghostly passage of a need or want or aspiration; merely, those 
molecules that copied did, and soon the face of the planet became transformed by 
the copying process. In time, the seas became full of these molecular collectives, 
forming, metabolizing, replicating . . . forming, metabolizing, replicating . . . 
forming, metabolizing, mutating, replicating. . . Elaborate systems arose, molecular 
collectives exhibiting behavior, moving to where the replication building blocks 
were more abundant, avoiding molecular collectives that incorporated their 
neighbors. Natural selection became a molecular sieve, selecting out those 
combinations of molecules best suited by chance to further replication. 

All the while the building blocks, the foodstuffs, the parts for later copies, 
were being produced, mainly by sunlight and lightning and thunder - all driven by 
the nearby star. The nuclear processes in the insides of the stars drove the 
planetary processes, which led to and sustained life. 

As the supply of foodstuffs gradually was exhausted, a new kind of molecular 
collective arose, one able to produce molecular building blocks internally out of 
air and water and sunlight. The first animals were joined by the first plants. The 
animals became parasites upon the plants, as they had been earlier on the stellar 
manna falling from the skies. The plants slowly changed the composition of the 
atmosphere; hydrogen was lost to space, ammonia transformed to nitrogen, 


methane to carbon dioxide. For the first time, oxygen was produced in significant 
quantities in the atmosphere - oxygen, a deadly poisonous gas able to convert all 
the self-replicating organic molecules back into simple gases like carbon dioxide 
and water. 

But life met this supreme challenge: In some cases by burrowing into 
environments where oxygen was absent, but - in the most successful variants - by 
evolving not only to survive the oxygen but to use it in the more efficient 
metabolism of foodstuffs. 

Sex and death evolved - processes that vastly increased the rate of natural 
selection. Some organisms evolved hard parts, climbed onto, and survived on the 
land. The pace of production of more complex forms accelerated. Flight evolved. 
Enormous four-legged beasts thundered across the steaming jungles. Small beasts 
emerged, born live, instead of in hard-shelled containers filled with replicas of the 
early oceans. They survived through swiftness and cunning - and increasingly long 
periods in which their knowledge was not so much preprogrammed in self- 
replicating molecules as learned from parents and experiences. 

All the while, the climate was variable. Slight variations in the output of 
sunlight, the orbital motion of the planet, clouds, oceans, and polar icecaps 
produced climatic changes — wiping out whole groups of organisms and causing 
the exuberant proliferation of other, once insignificant, groups. 

And then . . . the Earth grew somewhat cold. The forests retreated. Small 
arboreal animals climbed down from the trees to seek a livelihood on the savannas. 
They became upright and tool-using. They communicated by producing 
compressional waves in the air with their eating and breathing organs. They 
discovered that organic material would, at a high enough temperature, combine 
with atmospheric oxygen to produce the stable hot plasma called fire. Postpartum 
learning was greatly accelerated by social interaction. Communal hunting 
developed, writing was invented, political structures evolved, superstition and 
science, religion and technology. 

And then one day there came to be a creature whose genetic material was in 
no major way different from the self-replicating molecular collectives of any of the 
other organisms on his planet, which he called Earth. But he was able to ponder 
the mystery of his origins, the strange and tortuous path by which he had emerged 
from star-stuff. He was the matter of the cosmos, contemplating itself. He 
considered the problematical and enigmatic question of his future. He called 
himself Man. He was one of the starfolk. And he longed to return to the stars. 


Sagittarius, toward the center of the Galaxy. The dark lanes 
are dust clouds where complex organic molecules are being 
formed. Among these stars, there are some being bom and 
others dying. Innumerable inhabited planets probably circle 
the stars in this photograph. Courtesy, Hale Observatories. 


38. Starfolk 

II. A Future 

The story of the preceding chapter is a kind of scientific fable. It is more or less 
what many modern scientists believe on the basis of available evidence. It is the 
outline of the emergence of man, a process wending through billions of years of 
time and driven by gravitation and nuclear physics, by organic chemistry and 
natural selection. It tells how the matter of which we are made was generated in 
another place and another time, in the insides of a dying star five billion or more 
years ago. 

There are three aspects of the fable that I find particularly interesting. First, 
that the universe is put together in such a way as to permit, if not guarantee, the 
origin of life and the development of complex creatures. It is easy to imagine laws 
of physics that would not permit appropriate nuclear reactions, or laws of 
chemistry that would not permit appropriate configurations of molecules to be 
assembled. But we do not live in such universes. We live in a universe remarkably 
hospitable to life. 

Second, there is in the fable no step unique to our Solar System or to our 
planet. There are 250 billion suns in our Milky Way Galaxy, and billions of other 
galaxies in the heavens. Perhaps half of these stars have planets at biologically 
appropriate distances from the local sun. The initial chemical constituents for the 
origin of life are the most abundant molecules in the universe. Something like the 
processes that on Earth led to man must have happened billions of other times in 
the history of our Galaxy. There must be other starfolk. 

The evolutionary details would not be the same, of course. Even if the Earth 
were started over again and only random forces again operated, nothing like a 
human being would be produced - because human beings are the end product of 
an exquisitely complicated evolutionary pathway full of false starts and dead ends 
and statistical accidents. But we might well expect, if not human beings, organisms 
functionally not very different from ourselves. Since there are second- and third- 
generation stars much older than our Sun, there must be, I think, many places in 
the Galaxy where there are beings far more advanced than we in science and 
technology, in politics, ethics, poetry, and music. 

The third point is the most arresting. It is the intimate connection between 
stars and life. Our planet was formed from the dregs of star-stuff. The atoms 
necessary for the origin of life were cooked in the interiors of red giant stars. These 
atoms were forced together, to form complex organic molecules, by ultraviolet 
light and thunder and lightning, all produced by the radiation of our neighboring 
Sun. When the food supply ran short, green-plant photosynthesis developed, 
driven again by sunlight, the sunlight off which almost all the organisms on Earth, 
and certainly everyone we know, live out their days. 

But this cannot be the end of the fable. Our Sun is only approaching vigorous 
middle age. It has perhaps another five billion or ten billion years of stellar life 
ahead of it. 

And what of life on Earth and man? They, too, for all we know, may have a 
future. And if not, there are billions of other stars and probably billions of other 
inhabited planets in our Galaxy. What is the interaction between stars and life 
later on? 

The death of stars is taking astronomers into unexpected and almost surreal 
celestial landscapes. One of these is the supernova explosion, the death throes of a 
star slightly more massive than our Sun. In a brief period of a few weeks to a few 
months, such an exploding star may become brighter than the rest of the galaxy in 
which it resides. In super-novae, elements like gold and uranium are generated 
from iron. The supernovae are the long-sought Philosopher's Stone, converting 
base metals into precious metals. 

Having blown away most of its star-stuff - destined, some of it, to go into later 
generations of formation of stars and planets and life - the star settles down to a 
quiet old age, its fires spent, as a white dwarf. A white dwarf is constituted of 
matter in a state that physicists, with no moral imputation intended, call 
degenerate. Electrons are stripped off the nuclei of atoms. The protective shields 
of negative electricity are removed. The nuclei can move much closer together, 
and a state of extraordinary density results. Typical degenerate matter weighs 
about a ton per thimbleful. Some white dwarfs, properly considered, are vast 
stellar crystals able to hold up the weight of the overlying layers of the star. Some 
white dwarfs are largely carbon. We may speak of a star made of diamond. 

But for more massive stars, the white dwarfs - their embers slowly fading, 
decaying into black dwarfs - are not the end state. Degenerate matter cannot hold 
up the weight of a more massive star, and another cycle of stellar contraction thus 
ensues — the matter being crushed together to more and more incredible densities, 
until some new regime of physics is entered, until some new force surfaces to stop 
the stellar collapse. There is only one further such force known: It is the nuclear 
force that holds the nucleus of the atom together. This nuclear force is responsible 
for the stability of atoms and, therefore, for all of chemistry and biology. It is also 
responsible for the thermonuclear reactions in the insides of stars that make stars 
shine and, thereby, in a quite different way, drives planetary biology. 

Imagine a star more or less like the Sun, but a little more massive, near the end 
of its days of converting simple nuclei into more complex nuclei. It produces the 
last series of complex nuclear reactions it is able to - and then collapses. As its size 
decreases, it spins more and more rapidly, like a pirouetting ice skater bringing in 
her arms. Only when the density in its interior becomes comparable to the density 
of matter inside the atomic nucleus does the collapse stop. It is a simple matter in 
elementary physics to calculate at what stage the collapse will end. It ends when 
the star is about a mile across and rotating about ten times a second. 


Such an object is a rapidly rotating neutron star. It is, in truth, a giant atomic 
nucleus a mile across. Neutron star matter is so dense that a speck of it - just 
barely visible - would weigh a million tons. The Earth would not be able to 
support it. A piece of neutron star matter, if it could be transported to the Earth 
without falling apart, would sink effortlessly through the crust, mantle, and core of 
our planet like a razor blade through warm butter. 

Such neutron stars were theoretical constructs, the imaginings of speculative 
physicists - until the pulsars were discovered. Pulsars are sources of radio emission. 
Some of them are associated with old supernova explosions. They blink at us as if 
the beam of some cosmic lighthouse swept by us ten times a second. The details 
of the emission from pulsars are best understood if they are the fabled neutron 
stars. Because of the loss of energy to space that we observe, the rotation rate of an 
isolated neutron star must slowly decline, even though it is a stellar timekeeper of 
extraordinary accuracy. The observed decay of pulsar periods is just about what is 
expected from neutron star physics. 

The first pulsar to be detected was called, by its discoverers, only half impishly, 
LGM-i. The LGM stood for "little green men." Was it, they wondered, a beacon 
from an advanced extraterrestrial civilization? My own view, when I first heard 
about pulsars, was that they were perfect interstellar navigation beacons, the sorts 
of markers that an interstellar spacefaring society would want to place throughout 
the Galaxy for time- and space-fixes for their voyages. There is now little doubt 
that pulsars are neutron stars. But I would not exclude the possibility that if there 
are interstellar space-faring societies, the naturally formed pulsars are used as 
navigation beacons and for communications purposes. 

The state of matter in the inside of such a neutron star is still not understood. 
We do not know if a surface crust comprising a neutron crystal lattice overlies a 
core of liquid neutrons. Should the core be solid, starquakes are expected — a 
shifting of the matter under enormous stress in the interior of the star. Such 
starquakes should produce a discontinuous change in the period of rotation of the 
neutron star. Such changes, called "glitches," are observed. 

Some were disappointed to learn that pulsars were neutron stars and not 
interstellar radio communication channels. But pulsars are hardly uninteresting. 
Indeed, a star more massive than the Sun that fits into a sphere a mile across and 
rotates ten times every second is, in a certain sense, much more exotic than a 
civilization slightly more advanced than we, on the planet of another star. 

But there is another and much more profound way in which neutron stars and 
supernova explosions are connected with life. In a supernova explosion, as we 
have already mentioned, vast quantities of atoms from the surface of the star are 
ejected at very high velocities into interstellar space. In the case of the neutron 
star, there is, because of its rapid rotation, a zone, not far from its surface, which is 
rotating at almost the speed of light. Particles are ejected from that zone at 
velocities so great that the theory of relativity must be taken into account to 
describe them. Both supernova explosions and the high-velocity zone surrounding 


neutron stars must produce cosmic rays - the very fast charged particles (mostly 
protons, but containing all the other elements as well) that pervade the space 
between the stars. 

Cosmic rays fall on the Earth's atmosphere. The less energetic particles are 
absorbed by the atmosphere or deflected by Earth's magnetic field. But the more 
energetic particles, the ones produced by supernovae or neutron stars, penetrate to 
the surface of the Earth. And here they collide with life. Some cosmic rays 
penetrate through the genetic material of life forms on the surface of our planet. 
These random, unpredictable cosmic rays produce changes, mutations, in the 
hereditary material. Mutations are variations in the blueprints, the hereditary 
instructions, contained in our self-replicating molecules. Like a fine watch 
repeatedly hit with a hammer, the functioning of life is unlikely to improve under 
such random pummelings. But as sometimes happens with watches or bulky 
television sets, a random pummeling does occasionally improve the functioning. 
The vast bulk of mutations are harmful, but the small fraction of mutations that 
are an improvement provide the raw material for evolutionary advance. Life 
would be at a dead end without mutation. Thus, in yet another way, life on Earth 
is intimately bound to stellar events. Human beings are here because of the 
paroxysms in dying stars thousands of light-years away. 

The births of stars generate the planetary nurseries of life. The lives of stars 
provide the energy upon which life depends. The deaths of stars produce the 
implements for the continued development of life in other parts of the Galaxy. If 
there are on the planets of dying stars intelligent beings unable to escape their fate, 
they may at least derive some comfort from the thought that the death of their 
star, the event that will cause their own extinction, will, nevertheless, provide the 
means for continued biological advance of the starfolk on a million other worlds. 


The unification of the cosmos: A conjectural black hole rapid 
transit system. By Jon Lomherg. 


39- Starfolk 

III. The Cosmic Cheshire Cats 

The neutron star is not the most exotic inhabitant of the stellar bestiary. A star 
larger than three times the mass of our Sun is too big even for nuclear forces to 
stop its collapse. Once the collapse begins, there is nothing to stop it. The star 
contracts to one mile across and continues to shrink. The density passes that of the 
nucleus of an atom, and matter is further crushed together. The gravitational field 
in the vicinity of such a massive dying star continues to increase. Eventually, the 
gravity is so strong that not only is matter unable to leave the star, but light is also 
trapped. A photon traveling at the speed of light away from the star is constrained 
to follow a curved path and fall back upon the star, just as the Earth's gravity is 
too strong for any of us to throw a rock to escape velocity. Such stars are too 
massive for even photons to escape. Consequently, they are dark. They cannot be 
seen directly, because no light emanates from them. They are present 
gravitationally, but not optically. They are called "black holes." They are beasts 
akin to the smile on the Cheshire cat. They are enormous stars that have winked 
out but are still there. 

Black holes are basically theoretical concepts. They may sound no more likely 
than, and not nearly as charming as, the elves of Middle Earth. But they are 
probably there. In fact, much of the mass of the Galaxy may reside not in stars we 
can see, nor in the gas and dust between the stars, but in black holes peppering the 
Galaxy like the holes in an Emmenthaler cheese. 

The first black hole may have been found. Cygnus X-i is a rapidly varying 
source of X-rays, visible light, and radio waves. Its X-ray emission was monitored 
from NASA's UHURU satellite, launched from an Italian launch complex off the 
coast of Kenya. All the clues point to Cyg X-i's being a binary star, two stars 
revolving around each other in a regular and intricate waltz. From the motion of 
the one star we see, we can deduce the mass of the star we cannot. It turns out to 
be a massive star, perhaps ten times the mass of our Sun. Such a massive star 
should ordinarily be very bright. Yet there is no optical hint of its presence. The 
bright star in Cyg X-i is revolving about a massive object that is present 
gravitationally but not optically. It is very likely a black hole a few thousand light- 
years from Earth. 

Black holes may have their uses. What we know about them till now is entirely 
theoretical, not tested against the skeptical standards of observation. There are 
some strange possibilities that have been suggested for black holes. Since there is 
no way to get out of a black hole, it is, in a sense, a separate universe. 

In fact, our own universe is very likely itself a vast black hole. We have no 
knowledge of what lies outside our universe. This is true by definition, but also 
because of the properties of black holes. Objects that reside in them cannot 
ordinarily leave them. In a strange sense, our universe may be filled with objects 


that are not here. They are not separate universes. They do not have the mass of 
our universe. But in their separateness and their isolation they are autonomous 

There is an even more bizarre prospect. In one speculative view (Chapter 36), 
an object that plunges down a rotating black hole may re-emerge elsewhere and 
elsewhen - in another place and another time. Black holes may be apertures to 
distant galaxies and to remote epochs. They may be shortcuts through space and 
time. If such holes in the fabric of the space-time continuum exist, it is by no 
means certain that it would ever be possible for an extended object like a 
spacecraft to use a black hole for travel through space or time. The most serious 
obstacle would be the tidal force exerted by the black hole during approach - a 
force that would tend to pull any extended matter to pieces. And yet it seems to 
me that a very advanced civilization might cope with the tidal stresses of a black 

How many black holes are there in the sky? No one knows at present, but an 
estimate of one black hole for every hundred stars seems modest by at least some 
theoretical estimates. I can imagine, although it is the sheerest speculation, a 
federation of societies in the Galaxy that have established a black hole rapid- 
transit system. A vehicle is rapidly routed through an interlaced network of black 
holes to the black hole nearest its destination. 

At a typical place in the Galaxy, one hundred stars are encompassed within a 
volume of radius of about twenty light-years. If we imagine relativistic space 
vehicles for the short journeys - the local trains or shuttles - it would take only a 
few years' ship time to get from the black hole to the farthest star of the hundred. 
One year on board the relativistic shuttle would be occupied accelerating at about 
1 g, the acceleration we are familiar with because of the gravity of Earth. After one 
year at 1 g, we would approach the speed of light. Another year would be spent 
doing a similar deceleration at 1 g at the end-point of the journey. A galaxy with 
such a transportation system, a million separately arisen civilizations and large 
numbers of worlds with colonies, exploratory parties, and work teams - a galaxy 
where the individuality of the constituent cultures is preserved but a common 
galactic heritage established and maintained; a galaxy in which the long travel 
times make trivial contact difficult, and the black hole network makes important 
contact possible - that would be a galaxy of surpassing interest. 

I can imagine, in such a galaxy, great civilizations growing up near the black 
holes, with the planets far from black holes designated as farm worlds, ecological 
preserves, vacations and resorts, specialty manufacturers, outposts for poets and 
musicians, and retreats for those who do not cherish big-city life. The discovery of 
such a galactic culture might happen at any moment - for example, by radio 
signals sent to the Earth from civilizations on planets of other stars. Or such a 
discovery might not occur for many centuries, until a lone small vehicle from 
Earth approaches a nearby black hole and there discovers the usual array of buoys 
to warn off improperly outfitted spacecraft, and encounters the local immigration 


officers, among whose duties it is to explain the transportation conventions to 
newly arrived yokels from emerging civilizations. 

The deaths of massive stars may provide the means for transcending the 
present boundaries of space and time, making all of the universe accessible to life, 
and - in the last deep sense - unifying the cosmos.